The State Personnel Board shall provide for a performance management system for the periodic review and rating of the quality and quantity of work performed by classified employees. All agencies of the executive branch, exclusive of the Board of Regents of the University System of Georgia and of any agency which employed no classified employees as of July 1, 1996, shall provide for the review and rating of the quality and quantity of work performed by employees in the unclassified service in the same manner as employees in the classified service.