Paying up front is a mugs game. The trouble is most of the US JAR schools are doing the same so it is very tempting to go along with it.
Just ask yourself this question. If the discount for paying upfront is 10% for a 4 week course, then that is equivilent to an annual interest rate of approx 60%.
Now assuming that this is the case, what business pays that much interest and to whom? The answers are "someone desperate" and "someone not that reputable".
The truth is more like the typical "bargain scam". Overprice the product in the first place to "discount" it and make it look good value.
In either case the advise is to avoid, the former because the whole think looks flakey and in the second case because it looks like sharp practice. The aim is to prey on people who let rational thinking go on holiday the moment flying enters the thoughts.
This forum is awash with people who admit to having let the flying bug overwhelm commonsense and then have lost out.
Admittedly there are people who have got away with paying up front - perhaps they were lucky.
It is impossible to insure against these risks and that probably is the most telling comment.