All full-time employees of a postsecondary technical school formerly operated by a local board of education or area postsecondary technical education board as of July 1, 1987, or the date which the department assumes governance of the postsecondary technical school shall elect either to continue membership in the Teachers Retirement System of Georgia or to become members of the Employees' Retirement System of Georgia. Once such election is made by such personnel, the election is irrevocable during the tenure of employment with the Department of Technical and Adult Education or any postsecondary technical school governed thereby. All employees who are members of the Public School Employees Retirement System may elect to continue their membership in the Public School Employees Retirement System or to become members of the Teachers Retirement System of Georgia or the Employees' Retirement System of Georgia, if otherwise eligible under laws, rules, or regulations.