I would ask him if he enjoys the math that he does at school. If the answer is "it's too easy" or "too boring" (or whatever), I would advocate for him. I wouldn't wait for a child that young to complain, because sometimes they don't know to do that. I don't think that a kindergartner needs to learn division or exponents, but the problem is that if it is way too easy, and a child is forced to do math that they learned years ago, they learn to tune out or become careless. Then when they do actually confront challenging concepts, they don't know how to handle it. I think this concept applies whether a child is 5 or 9 or 13. At the back to school curriculum night, one of the teachers was talking about how the kids are not necessarily in their "grade level" for particular subjects, they are "putting the kid in the level that they need in order to learn." I thought that was a nice way of putting it.
I don't think that making sure a child is making progress is "pushing". If you were homeschooling, you wouldn't say "Ok, you know the whole curriculum for this year, so we don't need to do anything", or "we'll just go over this same stuff again even though you already know it." You'd find the right level for him, and that's what schools should be doing as well. When I asked about having my kids accelerated, it wasn't about needing them to get ahead, it was to spare them the torture of wasting their time on lessons/activities that did very little for them. If he already knows the material, you know there is some boredom involved, no matter how colorful or cute the shapes are. Plus the point of school is to learn, and every child should be learning in each subject. Your school sounds flexible, so I would take the opportunity to broach the subject and see what comes out of it.
