The board of school directors of each district shall provide the necessary grounds and suitable school buildings to accommodate all the children between the ages of six and twenty-one years, in said district, who attend school. Such buildings shall be constructed, furnished, equipped, and maintained in a proper manner as herein provided. Suitable provisions shall be made for the heating (including the purchase of fuel), ventilating, adequate lighting, and sanitary conditions thereof, and for a safe supply of water, so that every pupil in any such building may have proper and healthful accommodations.