Simple...Just DO NOT pay anything more then a couple of hundred in advance.
Just refuse, it's that simple.
Right now FTO's want/need your money. It is not unreasonable in anyone’s language, that as long as you are up to date to the point of having paid for the hour or so you are about to take, you should not be asked for a penny more.
As for integrated schools, at the very least an escrow account should be set up.
If they can't see the logic of that,... then walk away from the deal.
We are in difficult times (at least I agree with WWW on something!), no company is particularly safe, given the way that banks are now treating and charging their corporate clients.
I lost £250 many (many) years ago because I was 'conned' by a US FTO dear to PPRuNes heart!
You have no way of cost effectively arguing your case if you have paid up front and wish to dispute a bill....SO, DONT PAY UP FRONT!!!....repeat after me....DO NOT, PAY UP FRONT!!!