You need to take them to small claims court. But as capt pointed out the statutes of limitations may have run out. No lawyers needed in small claims, but you will have to find out what your max claim is for Texas and spend time and money on serving the flight school and paying court fees if you lose. Good luck, sheriff won't be able to do anything for you without legal notice to do so, they can't take sides until legally told to.
Small claims is designed for these kind of cases, lawyers aren't cost affective, you still need the situation resolved. They usually are capped between 5 or so thousand depending on the state.