This has nothing to do with the flight school. The Government is the one that F*cked up. If I was Bush I'd fire whoever was in charge of that department. If they can't even realize that they should have denied student visas to someone who is dead, not even just dead, infamous for their act, then they should not be running that department. Ax them! NOW!
Actually this gives ammo to the states that want to force flight school to make their students undergo federal background checks before they are allowed to fly. The biggest thing that most people don't see that most of the time the terrorist have no criminal background whatso ever, and their first would be the act itself. Unless we let the CIA start doing undercover ops inside terrorist orginizations there is no way we will ever know when they are going to strike.