In the second case, skipping ahead to learn with older kids may put my kids in classes with others closer to their current level of KNOWLEDGE, but not necessarily their learning SPEED (for new material). It sorta kicks the can down the road.
I realize that what I just typed comes off a little muddy.
Not at all.
As parent to a HG+ kiddo, we've pretty much tried
everything on Hoagie's lists of strategies.
The bottom line is that you HAVE to do multiple strategies at once with kids who are at higher levels of giftedness, or the fit is unbearably bad. But that doesn't mean that-- short of an ideal child being ideally homeschooled-- you can get a "good" fit for some of those kids.
Won't happen. CANNOT happen, probably, because to do so, you'd have to have an actual classroom of kids who are operating at roughly the same set of needs-- for material, for pacing, for learning/instructional style, for repetition. Oh, sure, if you're in a highly urbanized setting, you
might be able to get a child into an HG+ magnet setting, which is better by far... but even so, these kids have asynchrony as a
primary feature-- and that asynchrony is inherently idiosyncratic. So there IS no such thing as a learning environment of "peers" in the full spectrum of dimensions which matter in a classroom.
Does that make sense?
From a practical standpoint, then, what you (meaning, as a parent/advocate) are stuck with is choosing the
least-worst option available to you.
For us, that has been education at home for our DD13. In spite of the fact that my DD shares some of your middle child's oppositional tendencies when it comes to being "taught" anything.
It helps to have an outside agency the "authority figure" there-- for us that has been our virtual charter school. They are a better fit than the local school because they aren't as constrained re: acceleration or pacing (we can have DD do ALL of her math in one day, for example, to increase the RATE of delivery to better match what she finds ideal), and it is better than homeschooling because it doesn't make ME the bad guy re: requirements that my DD doesn't feel like meeting (Hey, it isn't MY assignment... but you'd better get to writing that essay if you don't want an F).
On the other hand, there is a LOT about it that is non-ideal:
a) large
volume of material stands in for actual increases in level or quality of instruction, which is basically the dreaded M.O.S. differentiation (in other words, it's NOT differentiation),
b) it's difficult to decouple subjects from one another sufficiently to actually match readiness levels, so students like my DD are learning WAY below their level in most subjects, and only really "on-level" in one or two, and even then, as you noted, it's not really at a pace that suits them well,
c) none of the 'pluses' of school exist either-- the social side, the sports and other activities are all "outside of school" in this model,
d) it doesn't eliminate the contentious environment of DD + me completely, because I'm still holding the whip and chair most days.
But it's the best we have.