Tenn. Code § 49-1512
Should any member having less than ten (10) years of creditable service, or four (4) years of creditable service for any member in an institution of higher learning, be absent from service more than seven (7) years in any period of nine (9) consecutive years after becoming a member or should he be employed by an employer operating a local retirement fund or plan or arrangement containing provisions for the retirement of teachers on a joint contributory basis or should he withdraw his accumulated contributions or should he become a beneficiary or die, he shall thereupon cease to be a member.
With reference to the above provision as to absence from service, on and after July 1, 1956, teaching service totaling at least eighteen (18) months during any period of nine (9) consecutive years after becoming a member shall be an absolute requirement to retain membership during any such period ending on any date on or after July 1, 1956. Provided that should such member with less than fifteen (15) years of teaching service in the public schools of Tennessee reenter the teaching profession, and become a member of the Tennessee teachers' retirement system prior to his sixtieth birthday and shall remain in the teaching service continuously for at least five (5) years prior to his sixtieth birthday and should such member repay any and all of his withdrawn contributions with interest at six per cent (6%) per annum from the time of his withdrawal of such contributions to the time of repayment of his withdrawn contributions, he shall be entitled to reclaim all his creditable teaching service in the Tennessee teachers' retirement system.
T.C.A. § 49-1512