[Kevin]

He's free to say what he wants. Freedom of speech is only a prohibition against governmental interference in the realm of ideas.

The government is not acting on his rights, the school, a private entity as far as I can tell is. He has to accept the consequences of his speech. If you tick the wrong people off, they'll no longer want to do business with you. That appears to be the case here. The school is free to admit and expel anyone they wish to.