I can accept him sharing a room, because if he went to an Oxbridge uni, a lot of the halls do have twin rooms.
But fraternities? No.
And he wouldn’t call it school. And whilst many universities are made up of colleges, he wouldn’t call it college either. Well, he’d say he attends such and such a course at such and such a college, or he’s at such and such a college. But he wouldn’t say “I’ve been at college all day” or “I go to college” or “When I was in college…”.
If someone asked him where he goes or went to school, he’d say either his secondary school or his prep school, depending on what he attended.