What we've said before.
If the school is going to pay you more interest then they would have to pay a bank to borrow the same money, then there is only one reason why they would do that:
They have tried to borrow money from a bank but failed because something or other about them was too dodgy for the bank to touch with a barge pole.
So, if you think you're better at evaluating the risks than a professional banker, then by all means go ahead - otherwise, lending several thousand pounds to a business that professional bankers have already decided is a bad risk sounds completely daft to me.