I was completely disengaged with classes during high-school. I found them too easy to study for and too boring to bother with. I'd show up to pass the tests, then skip again. It got bad.
A counselor helped me get into Running Start (college classes for college and high-school credits). I found the classes interesting and the atmosphere much more suitable to my brain's wiring. I ended up graduating with high honors and a near 4.0.
I don't know if it would help your son, but it might be worth talking with him about it if that—or a similar—program is available where you are.