There shall be permitted one wall or ground sign not exceeding 12 square feet located on the premises of places of worship, Sunday school buildings, public libraries, muesums, parish houses, buildings used exclusively by Federal, State, County, and local governments for public purposes, public, private and parochial schools, and public recreational and community center buildings. No fee shall be required in connection with the permit for such a-sign. No such sign shall be located closer than 15 feet to a property line or within the lesser of 15 feet or 1/2 the setback of the principal building, but in no event less than five feet, from a street right-of-way line.