Isa,
My DD8 is doing 4th grade math while in 3rd grade. She misses reading, so she makes up her 3rd grade reading while her teacher does the 3rd grade math lesson with the rest of the class. It's not ideal since DD8 loves reading and hates missing it (not to mention making her more of an outsider to her classmates), but she loves 4th grade math, so it's worth it to her. Have you considered trying such an arrangement? If you and she are OK with the downfalls, you may be able to talk the school into trying it at least for a test period.
