Honestly, he sounds a little like my DH. My DH was fine at school (I didn't know him then, but his grades tell the story), but as soon as he moved onto Uni he seemed to stop caring. Didn't turn up to classes, didn't do his work. He failed so many topics which is ridiculous cause he's super smart.He spent 4 years there and, if he was lucky, completed enough topics for half a degree. He swapped degrees once or twice in there too. Basically, he just wasn't interested in what he was doing.

In the end he just had to get out in the real world and get a job. He's ended up in banking and loves it and has moved well up the ranks (even without a qualification). Amazingly he just came to me last week and said he wants to study externally next year and work towards a banking degree.

I guess my point to the story is that maybe you should just let him leave school if that's what he wants and decide what interests him. It could be some other study or it could be an apprenticeship or a job. As he is smart he will probably find that that gets him a reasonable distance into his career and then he can possibly refine his skills a bit more in the future.