I don't think that this is a question about FAA flight validity, it's a question about American consumer law.
About which personally I know nothing, but finding a lawyer has never been difficult I he USA. Then again, their advice may be more expensive than just doing the flight again.
But my gut feeling is that if tbe OP did not take responsibility for ensuring that his flights met the requirements, that is probably his fault and his own problem, not the school's.