(a) The membership of this System shall be composed of all teachers employed after June 30, 1939 who become members as a condition of employment on the date they become teachers. Membership shall continue until the date a member becomes an annuitant, dies, accepts a single-sum retirement benefit, accepts a refund, or forfeits the rights to a refund.
     (b) This Article does not apply to any person first employed after June 30, 1979 as a public service employment program participant under the Federal Comprehensive Employment and Training Act and whose wages or fringe benefits are paid in whole or in part by funds provided under such Act.