When he is on his own, he is very happy, but when structure is added to the mix, he seems to have a breaking point. He has always had a strong dislike for rules, and now that I see the test results I wonder if that has something to do with him feeling rushed.
I think he likes to "ponder" and daydream a lot, and maybe that's related too.

He gets distracted at school I think. He brings home a lot of unfinished work that he then has to do at home - and he gets distracted at home too, so it takes him forever to get it done. Kind of unfair to him if he can't help himself.

so, yes, I think there's an issue, but I don't really think it's because he is slow at processing things. I just think he doesn't do well with structure (which sucks by the way...that's how I am too).