(a) Employees of each of the following-named private corporations, herein called state-aided institutions, shall be covered by the retirement system: The American School at Hartford for the Deaf, The Connecticut Institute for the Blind and Newington Children’s Hospital.

(b) Each person in the service of a state-aided institution shall become a member and shall make a monthly retirement contribution in the amount determined from § 5-161 as if he were a state employee. Such institution shall deduct his retirement contributions from his salary and pay them to the state.

(c) If the Retirement Commission finds that the rate of salary paid a member who is an employee of a state-aided institution, during the period of service upon which his base salary is determined for retirement purposes, exceeded the rate of salary paid by the state to its employees in a comparable category of service; or if the Retirement Commission finds that the aggregate salary increases of any such member during the last ten years of his service exceed the salary increases allowed by the state to its employees in a similar category of service; then, in either case, such excess shall be disregarded in determining the member’s base salary for the purposes of § 5-162. When such excess is so disregarded, the retirement contributions made by the member on such excess shall be returned to him by the state.

(d) No increase in the number of employees of a state-aided institution who may become members shall be made unless the Commissioner of Administrative Services approves such increase as to necessity and desirability.