The International Harvester S-Series "Schoolmaster" is a Type C (conventional) bus chassis that was manufactured by International Harvester and then Navistar International from 1979 to 1989. In 1989, the S-Series was updated and renamed the International 3800. It was used primarily as a cowled chassis for both school bus and commercial bus applications; it also was the basis for the front and rear-engine stripped chassis that International uses for bus applications as well.