Each school director of a school district having established a joint school or department with another school district, or, in case the affairs of such joint school or department are being managed by a joint school committee, then each member of such committee, shall receive for his necessary traveling expenses mileage at the rate of seven cents (7¢) per mile for the distance necessary to be traveled in going to and from the meetings of such joint board or joint school committee, not in excess, however, of twelve (12) meetings a year. Said amount shall be paid by warrant drawn on the joint board treasurer by the president and secretary of the joint board or joint school committee.