I'm with bzylzy. My DD10 loves to help her classmates in math. I think it helps her solidify her skills....you really need to understand something to teach it to a 4th grader!
But she gets no math instruction at her own level. At school that is. I'm doing math with her at home. On the bright side, her (team) teachers do realize they are not challenging her and she is not required to do the work the other kids do. She does that work when she wants a review and does the work from home the rest of the time. She keeps a math log for them as a way of being accountable.
The teachers wanted to send her to the 5th grade teacher for math, but the principal believes that you can challenge a kid by going deeper. I pointed out to him that that's what 5th grade math IS, 4th grade math, only deeper. Fell on deaf ears.
