On-premises sign for a school, camp, church, health-care facility, health-care service, private club or other institution of a similar nature, displaying the name of the institution and its activities or services, provided that the sign area shall not exceed 24 square feet, and provided that not more than one such sign shall be erected on any street frontage of any property in single and separate ownership. Said sign shall be set back at least 1/3 the distance of any required yard.