Yep, Dean will certainly got to school with Sam!
He might not at first, especially since Sam was a few years behind him in classes. John will want to keep Dean safe until they can get him cured, away from other grabby kids.
As Sam grows up and it starts to look bleak for Dean’s future as a regular-sized guy, Sam will convince him to come to school and keep his mind occupied instead of staying in the room and reading the same book on breaking curses. It’ll be healthier for Dean, and as Sam hits his growth spurt and no longer gets picked on by bullies (something he’ll avoid mentioning to Dean until Dean sees him with a black eye), he’ll be able to bring Dean safely with him.
Dean will complain, naturally. Still stuck with schoolwork.
Brothers Apart 