Depends on what manner and how severely disabled. Not that we need to know, don't say. But what to ask the schools would be very different depending on your condition. In the States there are schools that would give free courses for disabled and some that would charge extra. Again depends on the school and the disability.
If in that position I would not call up but would try to go in person so they see you are serious. Ask about the course and see if they fit your needs. If you are satisfied both you and they can work together then ask for help with the cost.
"I really want to learn from you, for I feel you are the best qualified. However, I would like to ask if there is any way to work out a discount on the fee."
Or how ever you feel comfortable in asking. You might even offer to work off part of the fee.