Try not to take this the wrong way but if he is having trouble keeping up with his studies now with only playing 7 hours of tennis a week. How is he going to be able to keep up with his studies when a coach expects 15 hours a week out of him?
Spring Break is coming up. Do yourself a favor and try to visit the campuses that he might be interested in. Since Spring Break for most colleges and high schools don't align, he will get a good idea of what the school is like during session.