One thing which really helped us was when we stopped viewing placement decisions as "right/wrong" and began looking at things through the lenses of "best we can do" and "least-harmful/greatest benefit" and realizing that all of it is fairly ephemeral because this is a child that we are talking about, so those needs are changing continuously and at variable rate.
I also agree with polarbear about digging more deeply to find out just what the limits are in terms of your options, though. At one end of that spectrum is one-stop-shopping at your default local public school. That works for mythical "average/normative" children. At the other end of the spectrum is radical homeschooling, where the curriculum is completely built AROUND the child's needs and interests each day.
Different parents will view the continuum with differing values, of course, which means that any two families are likely to evaluate those things differently even if they did somehow have the same exact child, which of course isn't the case anyway.
I mention that because your positive statements about public schooling's benefits may not be echoed by families that lean toward radical unschooling, but they are certainly valid to you, just the same.
(We agree with many of those positions ourselves, by the way, which is why we've kept our child within a system that we wrestle mightily with in light of the fact that it is a very poor fit for our child in many ways.)
Explore the different options for accommodation of HG students-- know what each strategy offers and what the down sides are. Know what the limitations are for you personally and for the school locally. (Telescoping, compacting, etc. I mean)
It is disheartening to discover that a grade skip that was supposed to "solve everything" hasn't. For HG+ children, though, it's also not an unusual thing. It's frustrating to realize that you're still having to advocate for more, and in the face of administration that looks at things as "Yes, but we've already got a checkmark next to 'special arrangements' for the year... So remind me, why are you here again?" They want a gold star for having done "so much" for your child, and they very definitely aren't always happy when they find out that it wasn't even close to meeting what your child actually NEEDS.
Be patient, but stand your ground if you KNOW that this gradeskip alone isn't enough. It sounds as though you do know it.
