In journalism, we used to say dog doesn't bite dog.
So as an instructor, flying school owner etc I am hoping this will be ataken as a general point, and not criticism of any particular school.
If you feel it is worthwhile paying up front, check the terms and conditions of the deal. IE what happens if you get a job in another country etc.
There is a reason you get a discount for paying up front, and that reason might be - in some business plans - that the "punter" disappears abroad.
But the bottom line for most people is don't pay up front. Just don't.
And if you do, check the terms and conditions.
And if you haven't seen and signed any, then check with your local trading standards and consider small claims court (as a business owner, the hassle of facing a small claims court action might well make me consider paying up!)
Very best wishes with your training (but one lesson to be learnt is that aviation is a small world and dogs don't bite dogs)
Since you are still a teenager and haven't had the lessons learned the hard way that I have had, here's another. Write what you want to say, such as resignation letters or tirades against flying schools/employers, put them in a drawer for 24 hours and then re-read them!