Nothing short of extremely flexible placement and pacing is truly appropriate for a student like that-- and the more inflexible the placement(s), the worse the fit gets. All of our troubles with the school come down to a lack of flexibility. ALL of them.
I'm a bit jaded at this point, but my basic feeling is that it is seldom the case that a "gradeskip solves problems." Maybe it makes the match between student readiness and curriculum less apparent, but it doesn't remove problems which actually exist in most cases. Why not? Because a school that is flexible enough to work for an HG+ child is going to do what they can without a gradeskip (mostly), and one that isn't is ONLY going to do the skip and then blame any future difficulties on the student's immaturity or the parent's unrealistic expectations. Yes, cynical of me, I realize, but that is how I tend to see this working for more people than not.
Mind. Blown.

I need to think about this statement some more, but it feels like it totally reframes the struggles that we have with DD8's school. Thank you.