Does your school do MAP testing or some similar test that lets your kid show above grade level knowledge? If yes, this will be a good tool in deciding about whether clustering will be enough wthout a skip. If there are other kids within your child's grade level who are performing at or near her level, then clustering may work. But if her scores are closer to the next grade level's cluster kids, you'll know that she'll likely do better with both clustering and the skip.
In our experience with DS8, he started 2nd after a grade skip with no clustering (because the tea her needed to get to know the kids), and the skip itself was nowhere near enough. Then a few months later, he was grouped with another kid for math, and that was a bit better, and he also had a few pullout groups with other kids from other classes, so not true clustering but more like differentiation with pullouts with the kids he would have been clustered with if clustering started at 2nd. None of those kids at grade level had similar scores to DS though, and so it was still not enough. We moved to a FT GT program, which has been great. But if we had stayed in the local school, where clustering started in 3rd, we probably would have given it a tru before another skip. The one skip was necessary though, and easier for the teacher. it's hard to differentiate so much. I do think clustering is the way to go if you don't have a FT GT program available.
