§ 503. Membership of system. 1. The membership of the retirement
system shall consist of the following:

a. All teachers who were teachers on or before the first day of
August, nineteen hundred twenty-one, who shall file with the retirement
board applications for membership, except those specifically excluded
under subdivision four of this section.

b. All teachers who were not teachers on or before the first day of
August, nineteen hundred twenty-one, except those specifically excluded
under subdivision four of this section.

2. The retirement board may, in its discretion, deny the right to
become members to any class of teachers whose compensation is only
partly paid by the employer or who are serving on a temporary or any
other than a per annum basis, and it may also, in its discretion, make
optional with members in any such class their individual entrance into
membership.

3. The membership of any person in the retirement system shall cease
when seven years have elapsed since the member has performed service as
a teacher which was credited with the system except as provided in
section five hundred twelve-a of this article, or upon the withdrawal by
a contributor of his accumulated contributions as provided in this
article, or upon retirement on a pension, or at death, except that the
membership of a teacher, who has not withdrawn his contributions shall
not be cancelled if he (a) has not had sufficient service to be eligible
for disability retirement, and proves to the satisfaction of the
retirement board that absence from service was caused by personal
illness constituting disability or (b) is eligible to receive a
retirement allowance from the system for other than disability.

4. Teachers who are members or who become members of a local district
pension system maintained under the laws of the state from
appropriations or contributions made wholly or partly by an employer
shall be excluded from membership in this retirement system.

5. A retired teacher receiving a retirement allowance for other than
disability may return to active public service. Any such retired teacher
returning to active service shall immediately notify the retirement
board of his intention. Except as otherwise provided in sections two
hundred eleven and two hundred twelve of the retirement and social
security law and section one hundred fifty of the civil service law, his
retirement allowance shall be suspended during the time he is in active
service. If such teacher has not elected an optional benefit, the
payments of his annuity so suspended shall be held in the annuity
reserve fund at regular interest, and upon the resumption of his
retirement allowance after again leaving the active service such
accumulated amounts shall be applied to increase the annuity otherwise
payable to him or in the event of his death while in active service such
accumulated amounts shall be paid to his estate or to such person as
last designated as the beneficiary of his accumulated contributions. If
such teacher has elected an optional benefit and dies while in active
service, the optional benefit in respect of his annuity shall be payable
as if no annuity payments had been suspended, but the optional benefit
in respect of his pension shall not be payable in excess of the
proportion that the cost of such optional pension, when measured by the
difference between his pension without optional modification and the
optional pension, is currently covered by the amount of the annuity
payments suspended while he is in active service, which difference shall
be paid during the period of his active service from the annuity reserve
fund to the fund from which his pension was payable. If, however, such
full cost of the optional pension is greater than the suspended annuity
payments, the teacher may elect upon returning to active service to pay
the amount of such difference directly to the retirement system to be
credited to the fund from which his pension was payable, and subject to
such payments monthly in advance, or at such other intervals as may be
agreed upon with the retirement board, the optional benefit in respect
of the pension shall be payable in the event the teacher dies while in
active service, as if no pension payments had been suspended. If the
suspended annuity payments are greater than such full cost of the
optional pension, the amount of such difference shall be held at regular
interest in the annuity reserve fund, and upon the resumption of his
retirement allowance after again leaving active service such accumulated
amounts shall be applied to increase the annuity otherwise payable to
him, or in the event of his death while in active service such
accumulated amounts shall be paid to his estate or to the beneficiary
nominated under the option.

6. Credit for service in war after world war I, which shall mean
military service during the period commencing the first day of July,
nineteen hundred forty, and terminating the thirtieth day of June,
nineteen hundred forty-seven, or during the period commencing the
twenty-seventh day of June, nineteen hundred fifty, and terminating the
thirty-first day of January, nineteen hundred fifty-five, or during both
such periods, as a member of the armed forces of the United States, of
any person who (i) has been honorably discharged or released under
honorable circumstances from such service, or (ii) has a qualifying
condition, as defined in section one of the veterans' services law, and
has received a discharge other than bad conduct or dishonorable from
such service, or (iii) is a discharged LGBT veteran, as defined in
section one of the veterans' services law, and has received a discharge
other than bad conduct or dishonorable from such service, or service by
one who was employed by the War Shipping Administration or Office of
Defense Transportation or their agents as a merchant seaman documented
by the United States Coast Guard or Department of Commerce, or as a
civil servant employed by the United States Army Transport Service
(later redesignated as the United States Army Transportation Corps,
Water Division) or the Naval Transportation Service; and who served
satisfactorily as a crew member during the period of armed conflict,
December seventh, nineteen hundred forty-one, to August fifteenth,
nineteen hundred forty-five, aboard merchant vessels in oceangoing,
i.e., foreign, intercoastal, or coastwise service as such terms are
defined under federal law (46 USCA 10301 & 10501) and further to include
"near foreign" voyages between the United States and Canada, Mexico, or
the West Indies via ocean routes, or public vessels in oceangoing
service or foreign waters and who has received a Certificate of Release
or Discharge from Active Duty and a discharge certificate, or an
Honorable Service Certificate/Report of Casualty, from the Department of
Defense or who served as a United States civilian employed by the
American Field Service and served overseas under United States Armies
and United States Army Groups in world war II during the period of armed
conflict, December seventh, nineteen hundred forty-one through May
eighth, nineteen hundred forty-five, and (iv) who was discharged or
released therefrom under honorable conditions, or (v) has a qualifying
condition, as defined in section one of the veterans' services law, and
has received a discharge other than bad conduct or dishonorable from
such service, or (vi) is a discharged LGBT veteran, as defined in
section one of the veterans' services law, and has received a discharge
other than bad conduct or dishonorable from such service, or who served
as a United States civilian Flight Crew and Aviation Ground Support
Employee of Pan American World Airways or one of its subsidiaries or its
affiliates and served overseas as a result of Pan American's contract
with Air Transport Command or Naval Air Transport Service during the
period of armed conflict, December fourteenth, nineteen hundred
forty-one through August fourteenth, nineteen hundred forty-five, and
who (vii) was discharged or released therefrom under honorable
conditions, or (viii) has a qualifying condition, as defined in section
one of the veterans' services law, and has received a discharge other
than bad conduct or dishonorable from such service, or (ix) is a
discharged LGBT veteran, as defined in section one of the veterans'
services law, and has received a discharge other than bad conduct or
dishonorable from such service, and who was a teacher in the public
schools of this state at the time of his or her entrance into the armed
forces of the United States, provided no compensation was received under
the provisions of section two hundred forty-two of the military law, and
who returned to public school teaching following discharge or completion
of advanced education provided under servicemen's readjustment act of
nineteen hundred forty-four, or who following such discharge or release
entered into a service which would qualify him or her pursuant to
section forty-three of the retirement and social security law to
transfer his or her membership in the New York state teachers'
retirement system, shall be provided as follows, any provisions of
section two hundred forty-three of the military law to the contrary
notwithstanding.

(a) Service in war after world war I as defined in this subdivision
shall be deemed to be service for all purposes of the retirement fund,
provided claim for such service shall be filed by the member with the
retirement board within two years following his return to active
teaching service or the entry of the member into a service which would
qualify him pursuant to section fifty-nine of the civil service law to
transfer his membership to the New York city employees' retirement
system or to the New York state employees' retirement system or the
fifteenth day of April, nineteen hundred sixty-seven, whichever is
later.

(b) For the purposes of computing final average salary, compensation
during any period of service in war after world war I shall be deemed to
have been at the member's rate of compensation in effect immediately
prior to such period, or based on additional increments due him if he
had continued teaching.

(c) Contributions paid by any member under the provisions of section
two hundred forty-three of the military law shall be refunded directly
to the member and the corresponding contribution paid by the district
shall also be returned directly to the district.

(d) On the retirement of a member with credit for service in war after
world war I as defined in this subdivision, there shall be transferred
from the pension accumulation fund to the annuity reserve fund a sum
equivalent to the contributions the member would have made to the
annuity savings fund had he contributed during his period of service in
war after world war I at the rate in effect immediately prior to such
period, or on additional increments due him if he had continued
teaching, with interest to the date of retirement, which amounts shall
be used to provide an annuity for him.

(e) In addition to the contributions required of employers to the
retirement system as otherwise provided, there shall be paid an
additional contribution to the pension accumulation fund to cover the
cost of the additional benefits covered by this subdivision. The
additional contributions shall be collected by increasing the regular
contributions of the employers in the same proportion as the liabilities
of the pension accumulation fund are increased by the adoption of this
subdivision.

7. A teacher, who was a member of the New York state teachers
retirement system but who withdrew his or her accumulated contributions
immediately prior to his or her entry into, or during his or her service
in the armed forces of the United States in war after World War I, who
(i) has been honorably discharged or released from service, or (ii) has
a qualifying condition, as defined in section one of the veterans'
services law, and has received a discharge other than bad conduct or
dishonorable from such service, or (iii) is a discharged LGBT veteran,
as defined in section one of the veterans' services law, and has
received a discharge other than bad conduct or dishonorable from such
service, provided no compensation was received under the provisions of
section two hundred forty-two of the military law, and who returned to
public school teaching in the state of New York following such discharge
or release, or following completion of advanced education provided under
servicemen's readjustment act of nineteen hundred forty-four, any
provisions of section two hundred forty-three of the military law to the
contrary notwithstanding, will be entitled to credit for service in war
after World War I, cost free, provided, however, that such credit will
not be allowed until he or she claims and pays for all prior teaching
service credited to him or her at the time of his or her termination of
membership in the New York state teachers retirement system, and
provided further that claim for such service in war after World War I
shall be filed by the member with the retirement board before the first
day of July, nineteen hundred sixty-eight.

8. A teacher who had been granted credit for service in war after
world war I as provided in this section and whose membership in the New
York state teachers retirement system subsequently ceased by reason of
withdrawal of his accumulated contributions will, upon rejoining the New
York state teachers retirement system, be entitled to the same credit
for service in war after world war I, cost free, that he was credited
with upon termination of his membership in the New York state teachers
retirement system, provided, however, that such credit will not be
allowed until he claims and pays for all prior teaching service credited
to him at the time of his termination of membership in the New York
state teachers retirement system.

9. Credit for emergency service on or after October first, nineteen
hundred sixty-one, shall mean active duty (other than for training) in
the armed forces of the United States as defined in title ten of the
United States code on or after October first, nineteen hundred sixty-one
and terminating on June thirtieth, nineteen hundred sixty-three or on
the date that no reserve component unit originally ordered into the
active service of the United States from the state on or after October
first, nineteen hundred sixty-one remains on such active service,
whichever sooner occurs, of any person who:

a. was a teacher in the public schools of this state at the time of
his entrance into such armed forces,

b. was a member of the New York state teachers' retirement system and
an employee of the state or of an employer at the time he entered such
armed forces,

c. (i) has been honorably discharged or released under honorable
circumstances from such service, or (ii) has a qualifying condition, as
defined in section one of the veterans' services law, and has received a
discharge other than bad conduct or dishonorable from such service, or
(iii) is a discharged LGBT veteran, as defined in section one of the
veterans' services law, and has received a discharge other than bad
conduct or dishonorable from such service, and

d. returned to public school teaching within one year following
discharge or release, or completion of advanced education provided by
the United States for education of Korean conflict veterans, or who
following such discharge or release entered into a service which would
qualify him, pursuant to section forty-three of the retirement and
social security law, to transfer his membership in the New York state
teachers retirement system. Such service shall not include any periods
during which compensation was received by the member for accrued
vacation and overtime credit or under the provisions of section two
hundred forty-two of the military law or section six of chapter six
hundred eight of the laws of nineteen hundred fifty-two.

Emergency service on or after October first, nineteen hundred
sixty-one, shall for the purposes of this article be deemed credit for
service in war after world war I.

10. Credit for certain World War II service. a. In addition to credit
for military service pursuant to section two hundred forty-three of the
military law and subdivisions six through nine of this section, a member
employed as a full-time teacher by an employer as defined in subdivision
three of section five hundred one of this article and who joined the
retirement system prior to July first, nineteen hundred seventy-three,
may obtain credit for military service not in excess of three years and
not otherwise creditable under section two hundred forty-three of the
military law and subdivisions six through nine of this section, rendered
on active duty in the armed forces of the United States during the
period commencing July first, nineteen hundred forty, and terminating
December thirty-first, nineteen hundred forty-six, or on service by one
who was employed by the War Shipping Administration or Office of Defense
Transportation or their agents as a merchant seaman documented by the
United States Coast Guard or Department of Commerce, or as a civil
servant employed by the United States Army Transport Service (later
redesignated as the United States Army Transportation Corps, Water
Division) or the Naval Transportation Service; and who served
satisfactorily as a crew member during the period of armed conflict,
December seventh, nineteen hundred forty-one, to August fifteenth,
nineteen hundred forty-five, aboard merchant vessels in oceangoing,
i.e., foreign, intercoastal, or coastwise service as such terms are
defined under federal law (46 USCA 10301 & 10501) and further to include
"near foreign" voyages between the United States and Canada, Mexico, or
the West Indies via ocean routes, or public vessels in oceangoing
service or foreign waters and who has received a Certificate of Release
or Discharge from Active Duty and a discharge certificate, or an
Honorable Service Certificate/Report of Casualty, from the Department of
Defense or on service by one who served as a United States civilian
employed by the American Field Service and served overseas under United
States Armies and United States Army Groups in world war II during the
period of armed conflict, December seventh, nineteen hundred forty-one
through May eighth, nineteen hundred forty-five, and who (i) was
discharged or released therefrom under honorable conditions, or (ii) has
a qualifying condition, as defined in section one of the veterans'
services law, and has received a discharge other than bad conduct or
dishonorable from such service, or (iii) is a discharged LGBT veteran,
as defined in section one of the veterans' services law, and has
received a discharge other than bad conduct or dishonorable from such
service, or on service by one who served as a United States civilian
Flight Crew and Aviation Ground Support Employee of Pan American World
Airways or one of its subsidiaries or its affiliates and served overseas
as a result of Pan American's contract with Air Transport Command or
Naval Air Transport Service during the period of armed conflict,
December fourteenth, nineteen hundred forty-one through August
fourteenth, nineteen hundred forty-five, and who (iv) was discharged or
released therefrom under honorable conditions, or (v) has a qualifying
condition, as defined in section one of the veterans' services law, and
has received a discharge other than bad conduct or dishonorable from
such service, or (vi) is a discharged LGBT veteran, as defined in
section one of the veterans' services law, and has received a discharge
other than bad conduct or dishonorable from such service, by a person
who was a resident of New York state at the time of entry into such
service and at the time of being discharged therefrom under honorable
circumstances, and who makes the payments required in accordance with
the provisions of this subdivision.

However, no military service shall be creditable under this
subdivision in the case of a member who is receiving a military pension
(other than for disability) for military service in the armed forces of
the United States.

b. To obtain such credit a member shall: (1) deposit in the annuity
savings fund a sum equal to the product of his required contribution
rate at time of entry into full-time New York state teaching service,
his annual full-time rate of compensation at that time, and the period
of military service being claimed, with regular interest, and (2)
deposit in the pension accumulation fund a sum equal to the product of
the employer's contribution rate exclusive of the rate for supplemental
pensions at the time of the member's entry into such teaching service,
his annual full-time rate of compensation at that time, and the period
of military service being claimed, with regular interest. Such deposit
must be made on or before October fourteenth, nineteen hundred
seventy-seven, provided, however, such member may elect to deposit such
amount over a period of time no greater than the period for which credit
is being claimed, in which case such payments must commence no later
than October fourteenth, nineteen hundred seventy-seven. If the full
amount of such payments is not paid to the retirement system at the time
of retirement, the amount of service credited shall be proportional to
the total amount of the payments made.

c. The credit for military service hereunder shall not be used to
increase a service retirement benefit if, at the time of retirement,
such member (1) is retiring from service with less than ten years of
full-time service credit or (2) is retiring with less than three years
of member service rendered subsequent to the date that he last became a
member of this system. Upon retirement, as specified in (1) or (2),
there shall be refunded to such member the amount of such deposit plus
accrued interest exclusive of the amount deposited to the pension
accumulation fund attributable to death and disability benefits.

d. (1) In the case of members who have transferred into this system
from another public retirement system within the state of New York,
their rate of contribution shall be computed as though they had been a
member of this system from the date of membership in the retirement
system from which they transferred.

(2) Any other provision of law to the contrary notwithstanding, the
rate of contribution to be used in calculating contributions to the
annuity savings fund pursuant to this subdivision shall be at the rate
of four per centum of earnable compensation for members whose date of
membership is on or before June thirtieth, nineteen hundred forty-eight
and at the rate of five per centum of earnable compensation for members
whose date of membership is on or after July first, nineteen hundred
forty-eight.

e. In no event shall credit be granted pursuant to this subdivision if
credit is granted for the same period of time pursuant to other
provisions of law.

f. No application for credit pursuant to the provisions of this
subdivision shall be honored if made on or after April fifteenth,
nineteen hundred seventy-seven.

10-a. Credit for certain World War II service. a. In addition to
credit for military service pursuant to section two hundred forty-three
of the military law and subdivisions six through nine of this section, a
member who joined the retirement system prior to July first, nineteen
hundred seventy-three, and who was not eligible for credit for military
service under subdivision ten of this section as a result of being on a
leave of absence without pay between July twentieth, nineteen hundred
seventy-six and October fifteenth, nineteen hundred seventy-seven or on
leave of absence with less than full pay between July twentieth,
nineteen hundred seventy-six and October fifteenth, nineteen hundred
seventy-seven, may obtain credit for military service not in excess of
three years and not otherwise creditable under section two hundred
forty-three of the military law and subdivisions six through nine of
this section, rendered on active duty in the armed forces of the United
States during the period commencing July first, nineteen hundred forty,
and terminating December thirty-first, nineteen hundred forty-six, or on
service by one who was employed by the War Shipping Administration or
Office of Defense Transportation or their agents as a merchant seaman
documented by the United States Coast Guard or Department of Commerce,
or as a civil servant employed by the United States Army Transport
Service (later redesignated as the United States Army Transportation
Corps, Water Division) or the Naval Transportation Service; and who
served satisfactorily as a crew member during the period of armed
conflict, December seventh, nineteen hundred forty-one, to August
fifteenth, nineteen hundred forty-five, aboard merchant vessels in
oceangoing, i.e., foreign, intercoastal, or coastwise service as such
terms are defined under federal law (46 USCA 10301 & 10501) and further
to include "near foreign" voyages between the United States and Canada,
Mexico, or the West Indies via ocean routes, or public vessels in
oceangoing service or foreign waters and who has received a Certificate
of Release or Discharge from Active Duty and a discharge certificate, or
an Honorable Service Certificate/Report of Casualty, from the Department
of Defense, or on service by one who served as a United States civilian
employed by the American Field Service and served overseas under United
States Armies and United States Army Groups in world war II during the
period of armed conflict, December seventh, nineteen hundred forty-one
through May eighth, nineteen hundred forty-five, and who (i) was
discharged or released therefrom under honorable conditions, or (ii) has
a qualifying condition, as defined in section one of the veterans'
services law, and has received a discharge other than bad conduct or
dishonorable from such service, or (iii) is a discharged LGBT veteran,
as defined in section one of the veterans' services law, and has
received a discharge other than bad conduct or dishonorable from such
service, or on service by one who served as a United States civilian
Flight Crew and Aviation Ground Support Employee of Pan American World
Airways or one of its subsidiaries or its affiliates and served overseas
as a result of Pan American's contract with Air Transport Command or
Naval Air Transport Service during the period of armed conflict,
December fourteenth, nineteen hundred forty-one through August
fourteenth, nineteen hundred forty-five, and who (iv) was discharged or
released therefrom under honorable conditions, or (v) has a qualifying
condition, as defined in section one of the veterans' services law, and
has received a discharge other than bad conduct or dishonorable from
such service, or (vi) is a discharged LGBT veteran, as defined in
section one of the veterans' services law, and has received a discharge
other than bad conduct or dishonorable from such service, by a person
who was a resident of New York state at the time of entry into such
service and at the time of being discharged therefrom under honorable
circumstances, and who makes the payments required in accordance with
the provisions of this subdivision.

However, no military service shall be creditable under this
subdivision in the case of a member who is receiving a military pension
(other than for disability) for military service in the armed forces of
the United States.

b. To obtain such credit a member shall: (1) deposit in the annuity
savings fund a sum equal to the product of his required contribution
rate at time of entry into full-time New York state teaching service,
his annual full-time rate of compensation at that time, and the period
of military service being claimed, with regular interest, and (2)
deposit in the pension accumulation fund a sum equal to the product of
the employer's contribution rate exclusive of the rate for supplemental
pensions at the time of the member's entry into such teaching service,
his annual full-time rate of compensation at that time, and the period
of military service being claimed, with regular interest. Such deposit
must be made on or before October fourteenth, nineteen hundred eighty,
provided, however, such member may elect to deposit such amount over a
period of time no greater than the period for which credit is being
claimed, in which case such payments must commence no later than October
fourteenth, nineteen hundred eighty. If the full amount of such payments
is not paid to the retirement system at the time of retirement, the
amount of service credited shall be proportional to the total amount of
the payments made.

c. The credit for military service hereunder shall not be used to
increase a service retirement benefit if, at the time of retirement,
such member (1) is retiring from service with less than ten years of
full-time service credit or (2) is retiring with less than three years
of member service rendered subsequent to the date that he last became a
member of this system. Upon retirement, as specified in (1) or (2),
there shall be refunded to such member the amount of such deposit plus
accrued interest exclusive of the amount deposited to the pension
accumulation fund attributable to death and disability benefits.

d. (1) In the case of members who have transferred into this system
from another public retirement system within the state of New York,
their rate of contribution shall be computed as though they had been a
member of this system from the date of membership in the retirement
system from which they transferred.

(2) Any other provision of law to the contrary notwithstanding, the
rate of contribution to be used in calculating contributions to the
annuity savings fund pursuant to this subdivision shall be at the rate
of four per centum of earnable compensation for members whose date of
membership is on or before June thirtieth, nineteen hundred forty-eight
and at the rate of five per centum of earnable compensation for members
whose date of membership is on or after July first, nineteen hundred
forty-eight.

e. In no event shall credit be granted pursuant to this subdivision if
credit is granted for the same period of time pursuant to other
provisions of law.

f. No application for credit pursuant to the provisions of this
subdivision shall be honored if made on or after October fifteenth,
nineteen hundred eighty.

11. a. If a retired member, receiving a retirement allowance for other
than disability, returns to active public service, except as otherwise
provided in sections two hundred eleven or two hyndred twelve of the
retirement and social security law, and is eligible for membership in
the retirement system, he thereupon shall become a member and his
retirement allowance shall be suspended in the same manner as provided
in subdivision five of section five hundred three of this article. In
such event, he shall contribute to the retirement system as if he were a
new member. Upon his subsequent retirement after at least two years of
service he shall:

1. Be credited with all member service earned by him since he last
became a member of the retirement system, and

2. Receive a retirement allowance which shall consist of:

(a) An annuity as provided in subdivision five of section five hundred
three of this article plus an annuity which is the actuarial equivalent
of any contributions made by him since he last became a member, and

(b) The pension which he was receiving immediately prior to his last
restoration to membership as provided in subdivision five of section
five hundred three of this article, plus a pension based upon the member
service credit earned by him since he last became a member. Such latter
pension shall be computed as if he were a new member when he rejoined
the system pursuant to the provisions of this subdivision.

b. Where such member shall have earned at least five years of member
service credit after restoration to active service, the total service
credit to which he was entitled at the time of his earlier retirement
may, at his option, again be credited to him and upon his subsequent
retirement he shall be credited in addition for purposes of computation
of the pension portion of the retirement allowance with all member
service earned by him subsequent to his last restoration to membership.
Such total service credit to which he was entitled at the time of his
earlier retirement shall be so credited only in the event that such
member returns to the retirement system with regular interest the
actuarial equivalent of the amount of the pension he received, or in the
event that such amount is not so repaid the actuarial equivalent thereof
shall be deducted from his subsequent retirement allowance.

c. Notwithstanding the foregoing provisions of this subdivision, a
retired member who is receiving a retirement allowance for other than
physical disability, and who returns to active public service, may elect
not to be restored to membership in the retirement system until he has
rendered one year of service following his return to public service. In
such event his retirement allowance shall be suspended during such year
of service in the same manner as provided in subdivision five of section
five hundred three of this article. Upon restoration to membership
following completion of such year of service, his service in such year
shall be deemed to be service while a member for purposes of subdivision
b of section five hundred twelve of this article. He may purchase member
service credit for such year, which shall be deemed earned member
service credit.

d. Notwithstanding any other provision of this article, a retired
member who rejoins the system under the provisions of paragraphs a or c
of this subdivision shall only be entitled to a death benefit according
to the provisions of paragraph two of subdivision b of section five
hundred twelve of this article and of no other subdivision thereof and
for the purposes of said paragraph two of subdivision b of section five
hundred twelve the credited service as a teacher shall be service as a
teacher credited since last joining the system.