Boys' School(Les Disparus de Saint-Agil)

In a college, three friends form a secret society. There objective - going to America. A night, after one of their secret meetings, one of them see a man coming out from a wall. Then the day after he talks about it, he disappears. Then the second one vanishes. Are they gone to their dreams? That's when the art teacher is murdered. Suspicions now are too high so the third one decides to investigate.