Also, the fact that his visa is valid for one year, means nothing if the school drops him as a student. Visa is not a document that grants your stay in the USA, but it is a document that allows single or multiple entries in the USA ( depending on what is specified on that visa). In other words, if his school dropped him, his M-1 visa that expires in 1 year, does NOT permit him to stay legally in the USA, because he lost his legal status, once his school dropped him. Of course, in practice, there will be some sort of a grace period (30-60 days) so he could leave the country legally.