Other provisions of this subchapter to the contrary notwithstanding, a school janitor, bus driver, or cafeteria worker who is enrolled in one (1) of those positions as a member of the Arkansas Public Employees' Retirement System and later is promoted to a position as school maintenance worker or supervisor, as bus mechanic or as transportation supervisor, or as cafeteria manager, respectively, shall continue to be a member of the Arkansas Public Employees' Retirement System as long as he or she is employed in one (1) of those respective capacities.