The services described in Section 1703 shall, except in advisory services in school business administration activities, clerical, accounting, and stenographic services, be performed by persons who hold a valid credential, or a life diploma based thereon, authorizing administrative services.

Any person who is, and continuously since September 7, 1955, has been, employed in the office of a county superintendent of schools and is performing any of the services described in Sections 1703 and 1704 may continue to perform such services without possessing the credential otherwise required as long as he remains continuously employed in his position.