High Time (1960) on Netflix

Widower and hamburger restaurateur Harvey Howard decides to go to college at 51 years of age. Resisting the easy path, he insists on not receiving preferential treatment, and lives in a dorm like the other students despite the disapproval of his grown son and daughter. As the years pass, and he gets involved in study sessions, fraternity initiations, and sporting events, he begins falling in love with Professor Gautier, the French teacher, but doesn't consider re-marrying appropriate.