I was one of those kids.

Did well in class, participated, and my grades trended downwards as the school year went on.

A lot of it was undiagnosed ADHD, which didn't work well with the repetitive nature of much public schooling. OK, let's do polynomials. Start with two terms...then three...then four...and on and on. I lost interest after three. Of course, then I didn't study or practice and did poorly on tests.

I grasped the concepts, but couldn't be bothered to study.

I had the same problems in other subjects. I'm a big history nerd. I could write a huge essay on the causes of WW1, but instead the tests were "what was the date of the assassination of Archduke Ferdinand...".

We also read the Hobbit as a grade 8 class book. First question on the test? "Name all the dwarves that were at Bilbo's party...". It took me a decade to re-read it and get into Lord of the Rings.

I've actually thrived in the "real world" because I can quickly grasp concepts and with a combination of grit managed to make a great tech career. I was lucky with timing though. Had I been born a 5 years later, the career path wouldn't have worked.

> put him in a classroom setting, for something he doesn't really care about, and he just won't do the work.

Coming from a family of people assumed to be like this, and having friends in similar situations. Rarely are they actually disinterested in the subject, but are disinterested in how it was taught and self conscious of their perceived understanding of the subject. It's easier to say you don't care when it comes up.

I'm guessing your past this option but you could try a Montessori classroom -- less structured and allows children to chase their own pursuits. My sense is its stronger for years 1-6 as opposed to later years. Also it doesn't feel like Montessori tries to grind down the children - school/teachers dependent for sure (same could be said for other systems).