Section 31C. Any officer or employee of the commonwealth, employed in a non-teaching position in any school or college within any department of the commonwealth, whose regular service is rendered between September 1 and June 30, may be granted the vacation leave to which the officer or employee is entitled either during the period of the officer or employee's regular service, or after the expiration of said period, as is determined by the employing authority of such officer and employee. Funds made available by appropriation for the payment of personal services required in the operation and maintenance of such schools shall be available for the payment of vacations, which, under the authority of this section, are granted to be taken after the termination of the period of regular service of an officer or employee subject to this section.