My DD complains because they use the spiral method, which is great when in 3rd grade because it introduces concepts earlier than most, but to her there is no difference between 2-digit and 3-digit division. So, there are very few new concepts each year.
Last year, I had the WISC-IV and EXPLORE test results and said the options were grade skip or we are taking her home. There was much resistance until I walked in 3 weeks later with her math tests. There was still concern until she had straight As at the first 9 weeks and "Excellence"( 96+ average) in all but one subject. Given that we are at the same place as last year and we took our younger one out of school last year to homeschool, they are not surprised. Last year I told them that she was bored out of her wits and I wasn't going to do that to her. We had the support of her teachers with the grade skip because she would finish her work in 10 min, when the time to finish it was 50 min. before approaching the principal, I made sure that I had ample evidence.