I would ask if they have end-of-the year assessments for math, for each grade (or even quarter or semester assessments). DS is in third and was given the end of the year third, fourth, and fifth grade assessments and passed them all with at least 85 percent accuracy, so they put him in 6th grade for math. They do this with all the kids in the school, so I didn't need to argue or ask about anything (I was simply informed that DS was going to a 6th grade classroom for math), but you could argue for that on an individual basis. If that doesn't work, ask if he can pre-test for units and if he gets a certain score, skip that unit. If he does pass out of it, figure out what you want him to do. DS did Khan Academy (before he went to current, flexible school). It wasn't the ideal situation, but at least he wasn't forced to sit through endless lectures about how to figure out 2+2. I'm guessing you probably have a battle on your hands. You may want to go directly to the principal and ask what they do for kids who are very advanced in math. I'm sure you did this already, but make sure the teacher knows that you don't agree with the counting assessment, and your DS must simply have been not paying attention/made a silly error.
