I'd try to approach the situation in this way:
1) document every call, every complaint from school. Be sure to ask the teacher and your ds what type of work was being done when the behavior occurred, and be sure you know what your ds' objection to it is.
2) Advocate for more advanced work now. There are different things you can do - one suggestion is to ask the teacher that your ds only be required to demonstrate he understands a concept by completing every other problem (or some subset) on each worksheet, then allow him to work on differentiated challenging work that either the teacher provides or you provide. Another thing you could request is pre-test in math and allow him to work independently on challenging math during the class' math time if he scores high enough to demonstrate knowledge on the pretest. If the teacher argues that if she does this for one student, she should do this for others, suggest that's ok - do it for others too. Chances are your ds isn't the only student in class ready to move forward in math.
3) You can volunteer in the classroom - one thing that another parent did in our elementary school when her ds was clearly ready for a higher level of math than he'd get in his regular classroom was to volunteer once a week to teach a pull-out group of the higher-achieving math students advanced-for-the-classroom concepts.
4) Lastly, continue to advocate. When the calls come home, make a suggestion re something the teacher could do to prevent a future similar situation. If the teacher doesn't follow through with the differentiation, just keep keeping track of it, and after a little bit of time has passed, and things aren't improving, request a meeting. Call in your school's gifted coordinator if there's one on staff. Make a call to the district coordinator to ask what your options are. Just keep plugging away. I wouldn't let it sit for a year.
5) Last thing, I do think it's important to teach children respect. Granted, the classroom isn't a perfect fit for your child - but it's most likely not for a lot of other children either. Let your child see that you are advocating for a better fit - that's a great lesson. But at the same time let him know you expect him to be respectful of his teacher. I don't entirely see this the way Dude does, that this situation is somehow partially the fault of the teacher or lack of respect from the teacher. I think it's important that our children understand they are not the only child in the classroom, and it's not easy to teach a class of 20+ kids and make the curriculum appropriately challenging and interesting for every child all the time. You can talk to your ds about appropriate ways to respond and actually communicate to the teacher what the real frustration is. Rather than refusing to do work, share with your ds that if he actually does the work, then explains calmly to the teacher that it was easy and he'd like more challenging work etc - it may not result in anything, but it's a more promising way to approach a challenging situation.
polarbear