Ohio Revised Code Title I. State Government § 145.03

(A) A public employees retirement system is hereby created for the public employees of the state and of the several local authorities mentioned in section 145.01 of the Revised Code. Except as provided in division (B) of this section, membership in the system is compulsory upon being employed and shall continue as long as public employment continues.

(B) A student who is not a member at the time of his employment with the school, college, or university in which he is enrolled and regularly attending classes may elect to be exempted from compulsory membership and a student who is a member may elect to have his employment with the school, college, or university in which he is enrolled and regularly attending classes exempted from contribution to the retirement system. An election to be exempted from membership or contribution shall be made by signing a written application for exemption within the first month after being employed and filing the application with the public employees retirement board. All applications, when approved by the public employees retirement board and filed with the employer, shall be irrevocable while the employee is continuously employed by the school, college, or university and regularly attending classes.