All of this is to say that if your son is that advanced in math and you're already homeschooling some subjects, I don't think that placement in a regular ed math classroom (as opposed to a gifted classroom) three grades up is the best answer. And that they're using Everyday Math makes it worse. Unless you're planning to use the classroom experience as supplemental while you do the primary teaching at home using a solid program (like Singapore math or AoPS), I would pass on this opportunity.

We are using this class as a supplement to what we are doing at home. Basically our situation is: DS does not want to homeschool full time. We are looking for ways to make his mornings at school a little more interesting. He has all specials and math in the mornings. The afternoons he comes home. Up until now, I was sending in math work for him to work on by himself during math time. He strongly preferred to work with other children, so we were looking for a way to do that. We are also hoping to give him a bit of a "resting" point as he tears through the curriculum at lightning speed. At his current rate, he will doing algebra probably next year, so we are looking at this 5th grade math class as a way to make sure he's really got all of his gaps filled. He will NOT continue with this group next year. And this class will stop learning topics in April as they spend a month preparing for state test review. So, we are looking at about 6 months with this class.