Tenn. Code § 8-3706
Notwithstanding any provision or provisions of any other section of chapter 37 of title 8 or any other law, to the contrary, any "teacher" who has been a member of the Tennessee teachers' retirement system, and who later became employed as a member of the professional staff of the Tennessee state department of education and who became a member of the Tennessee state retirement system, shall, upon giving due notice, in writing, to the Tennessee state retirement system, and to the Tennessee teachers' retirement system, with the approval of the state commissioner of education, be reinstated as a member of the Tennessee teachers' retirement system, provided that when such "teacher" retires his retirement benefits and allowances shall be calculated as though the time which he served in the Tennessee state department of education while he was a member of the Tennessee state retirement system shall be counted as though he had been a member of the Tennessee teachers' retirement system during such period of time; provided that such "teacher's" contributions to the Tennessee state retirement system for such period of time, plus the accrued interest thereon, shall be transferred, upon such due notice in writing and approved by the state commissioner of education, to the Tennessee teachers' retirement system, and, provided further, said "teacher" shall pay to the Tennessee teachers' retirement system any additional amount, above the amount so transferred from the Tennessee state retirement system, which amount may be required to equal the amount of the total contributions which said "teacher" would have made to the Tennessee teachers' retirement system during his service in the Tennessee state department of education while he was a member of the Tennessee state retirement system; provided, further, that the employer's contribution for such "teacher" for such period of time shall, likewise, be transferred by the Tennessee state retirement system to the Tennessee teachers' retirement system.
It is hereby declared that the purpose of this section shall be to provide to such "teacher" the full benefits of the Tennessee teachers' retirement system, based upon his employment by the state department of education, the same as if such "teacher" had remained in the Tennessee teachers' retirement system, when he entered upon his services in the Tennessee state department of education, instead of having become, at that time, a member of the Tennessee state retirement system.
T.C.A. § 8-3706