I'm a HUGE fan of compacting for kids like this. That's exactly what we've chosen to do with our DD.
SHE, on the other hand, has sometimes been quite a reluctant participant. But a lot of that is that she "already knows" most of the curriculum... so while I'm sympathetic on that score, there is also plenty that she is learning that she DOESN'T yet know... and those meta-skills (like how to construct a reasonably coherent outline, a bibliography, MLA formatting, citations for different types of writing, how to write a lab report, how to ask for help from a teacher, etc) are what she is actually learning instead.
Those things are pretty valuable in and of themselves! We've not done a lot of out and out 'skips' because part of the social fabric of relating well to peers is about shared experiences. So skipping high school biology by testing out of it might have been an option, but then it leaves her as a college student without a way to "relate" to her classmates about the stuff that goes on in that class.
