Class (1983) on Netflix

Jonathan, a naive country boy, gets a scholarship to a classy prep school, where he rooms with suave, rich and handsome Skip. Skip decides it is his duty to see that Jonathan loses his virginity, so he sends Jonathan to Chicago, where Jonathan meets Ellen, a beautiful older woman, and they be- gin an affair which ends abruptly when Ellen discovers Jonathan is 17. During Christmas break, Jonathan visits Skip's house and discovers that Ellen is Skip's mother. Ellen tells Jonathan to leave when he rejects her advances, but then begins calling him and begging to see him. Finally, Jonathan agrees to meet her and plans to end the affair, but Ellen seduces him--and that's when Skip, who followed Jonathan, discovers them.