I have to agree with those who see this as way too much math, when the math itself is just busy work. He should not have to do all the regular work, plus the extra sheets, plus the homework, when he is not learning from any of it. No wonder the poor little thing is rebelling!
If at all possible, could you talk to the teacher and negotiate down the volume? Ideally, he'd skip the regular work, but if the teacher balks (and they often do) suggest that on the regular work, he does the last row/ last couple/ hardest problems, and then gets to move immediately to something more challenging. Ditto for homework, eliminate if he doesn't need the practice, or do the last couple to prove it, and done. Ideally, ideally, let him bring some AoPS to school instead!
(What I actually did around this age when we got regular math homework was to pick out the hardest question or two, orally check with DS (who has writing issues) whether it was completely obvious (and it always was), and then write on the paper "Reviewed orally with parent, signed X". I could usually do it over 1-2 bites of dinner. Done. On the rare occasion it was a new topic, I'd make him actually do the last couple in writing, just to be sure.)
I've also learned the hard way how important it's been to start building an understanding with my kids about stuff like this as early and consistently as possible. They need to know I've got their back, that I'm listening, that I get it, and that I am actively working on their behalf to change the things at school that are making them most miserable. Some kids shrug off the repetitive worksheets, whip through them and move on. Others feel crushed by the make-work. The battles you pick depend very much on the individual kid. The kids themselves need to know that we have to pick our battles, and also that there are some things we can't change and just have to live with. They are more willing to deal with those knowing we are changing what we can.
