The plan is for him to start his hours now at 15 so that in July when he turns 16 he can go solo.
If you do this, make sure the hours are frequent, and at regular intervals. And forget putting pressure on him to do it at 16, it's not even worth it.
Ensure he is aware of flying jobs other then airline pilot. It's not the only option out there.
Oh, and because he's still a kid, make sure he lives his teenage years in a good way, not just making them 100% about flying. Because otherwise, alot of catching up may want to be done at some point, and it better come at a good time!
Cheers