He's probably going through what most people his age are going through, he stopped giving a shit about HS because he figured out it's all a game that he doesn't seem interested in playing. Pointless busywork in a large majority of classes. What he hasn't figured out is that you have to play the game to succeed later in life.. but right now with his age, the future doesn't really matter to him yet.
The answer isn't just to simply take shit away, that's an awful motivation technique from lazy parents that will only fuel his discontent with the world around him even more. The answer is to be honest with your son and explain that while it seems that things aren't important now, they will be later in life and you just want what's best for him. Just be straight up about it, if you don't pull your shit together and play the game and make the grades you need to get into the next game (college) then you'll be at a huge disadvantage later in life when the time comes. If he does not respect you enough by this point to listen to you then it's already too late and he'll have to fall on his own and learn from it.