Compensations of the teaching and other technical forces of the school department and employees of the Steinhart Aquarium and law library departments, construction employees engaged outside of the City and County, part-time employees, and inmate and institutional help receiving less than $50 per month, shall be fixed by the department head in charge thereof, with the approval of the board or commission, if any, in charge of the department concerned and subject to the budget and appropriation provisions of this Charter; provided that part-time employees shall be recorded as such by a principal executive, only with approval of the civil service commission and, when so recorded, shall be noted as part-time on payrolls, budget estimates, salary ordinance and similar documents.