Perhaps rather than up front demanding the grade skip, you could argue that the current curriculum is not working for her and request some out of grade level testing? Or you could do the testing on your own, Northwestern's Talent Search will take 3rd graders for the Explore, but maybe you don't want to wait that long. Or do they use MAP testing? If so, then they should already have that information.
Anyways, focus on the fact that the current situation is not working and demand changes based on these out of grade level assessments. At minimum, subject accelerations should be provided.
And if there are others that are "brighter" than her, than they must be having similar problems too. In which case, they should advance the curriculum for all, right? I see where they are coming from, but if they have many kids in their program who could legitimately request grade skips, then they probably need to step up the instructional level, right?
Another thought is this: perhaps the difference between her and these "brighter" kids is that maybe she thinks differently and they think more traditionally? If that is the case, then she has different needs and these needs should be met regardless of how well it is working for the others.
