I just had a big crisis along these lines when I realized my previous plan of just having DD work ahead as much as she wanted might end up in her repeating a bunch of stuff. I had optimistically thought that we would be able to get her into a school where they would let us do independent study, but I'm now starting to believe that will not be the case and she will be expected to lock-step with the standard curriculum (so even having to re-do pre-algebra before she even gets back to repeating algebra). A local education expert advised that I call the math departments of the schools we were thinking about for middle school to ask them whether acceleration/ independent study were acceptable, because as he pointed out you can probably take their word for what they will do. Excellent idea, I thought--only flaw is they're not calling me back. Did I just become one of 'those parents' by politely asking the question? Heaven forbid. I'm choosing to assume that if DD gets into their school they might return my call, but maybe they won't. And for the private schools there's a test ($) and a length application and an application fee ($$)--so it would be nice to know what to expect before we go through all that.
I am going to think hard about this too and probably try to refocus on the parallel route--we just started AoPS and Alcumus and DD loves it. She's working on Intro to Probability and Counting independently at her current school and I may try to look for another parallel outside thing to work on at home rather than continuing with the AoPS algebra--but it is very disappointing to basically be holding her back. Hopefully though she won't lose her love of math by having to do things this way.
And just as an aside--we only do math at home when she doesn't have another afterschool activity; this works for now because she doesn't have homework. I suppose things will slow down even more once she starts getting homework, but as long as she's happy and learning *something* I guess that's enough.