I say just go to school, don't say anything and see what happens. They might not bother checking. If they do, tell them you already have your own insurance and don't need theirs. If they actually look as though they're going to throw you out of the school for not buying their overpriced insurance plan, talk to a lawyer. But you'll be in a much better position if you start actually going to the school, since kicking you out (as opposed to not letting you in) will make them look very bad, and is more likely to be illegal.