Eventually, we simply flat out told the teacher that our son wouldn't be participating in the homework nor any in class math work until they were teaching something that would be new grounds for him. It wasn't a threat, it wasn't being difficult, it was simply informing them so they'd know.
This is what we did last year at this time when DS's teacher kept sending home the 1st grade 2+3 homework. The teacher told me that she wanted him to do it so that his handwriting improves. If she wanted his handwriting to improve there are more appropriate things she could have given him! I wrote her an email saying that DS would not be doing the homework anymore and eventually she stopped sending it. I started sending in work that I chose myself as his homework. I didn't tell DS to not do the classroom work since I thought that would send him the wrong message, but it was tempting. Eventually we just took him out.
