All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
If the training fees which the school proposes to the public is immediate payment, or delayed payment with added value that does not increase over time, then this is lawful provided the amount due does not increase if the person fails to pay in the fixed time for payment.
Now if the increase in the delayed payment changes with time or if there is a value added for failure to pay on time, then this is forbidden as it includes Riba (interest and/or usury).
Allaah Knows best.