Section 32. The school committee shall elect a superintendent of schools annually, except as provided in section forty-one of chapter seventy-one, and may, under chapter thirty-one, appoint, suspend or remove at pleasure such subordinate officers or assistants, including janitors of school buildings, as it may deem necessary for the proper discharge of its duties and the conduct of its business; it shall define their terms of service and their duties, and shall fix their compensation. No member of the school committee shall, while a member thereof, hold any other office or position in the school department the salary or compensation for which is payable out of the city treasury. The committee shall organize annually on the first Monday in January, and shall elect one of its members as vice chairman, who shall preside at all meetings of the committee at which the mayor is not present.