This is a hard one! Does he have the same problem waking up if it’s to do something “fun”, i.e., what if you had to leave for Disneyland early the next day? Would he be able to get up?
A couple of things came to mind as I read your post, for whatever they’re worth:
If he wakes up when you shake him awake, then maybe that’s the best solution for now, except maybe you add a rule that when you shake him awake, he has to get up on his feet right at that moment–no laying there or laying back down after you walk away. (and if it were me, if he does go back to sleep, is late and I had to drive him to school, he would have to pay me “taxi fare”–Maybe you can find out what an uber or lyft would cost from your house to school (or an equivalent mileage) and charge him that. If he doesn’t have any money, tell him that’s okay, he can pawn something to pay you, or do chores in an amount equal to the hourly rate.) I have found that often kids find new ways of doing things if the consequences of staying the same wind up being too painful. In other words, if he has to pay for his decision to be late, I’m betting he’s going to be much more inventive about coming up with ways to get up and stay up so can avoid those consequences.
Another idea is to see if his high school will consider doing a partial schedule, e.g., Talk to the school counselor about the possibility of scheduling all his core classes later in the day at school and then maybe do some of his other classes online. That way, he can sleep in and won’t miss his classes that count the most on his transcripts. But in this scenario, he’d need to figure out how he’d get to school. (And this scenario doesn’t build in tools and techniques that he’ll need to be able to hold down a job in the future.)
Which brings me to what I think is the most important thing: preparing him for adulthood. Somehow you need to shift this to make him see this is HIS problem, not just yours so that he can a) see it as a problem and b) be involved in the solving of the problem and c) feel the sting of the consequences if he doesn’t.
Hang in there and good luck!
Parenting Coach, school counselor, author, mom of adult son with ADHD