We just started compacting precalc for our 9th grade twins, and so far it is going well. They work independently (on math) during their math period at school, and take the tests when ready (much more frequently than in the regular class). Our goal is for them to complete 2 yrs of math (precalc and AP Calc AB) in one year, so that they can then do Calc BC next year in a regular class.
So far (we started a month and a half ago), it is working well. The kids realize they've gotten a special deal from the school and that motivates them to make it work. Another benefit is that we are effectively partially homeschooling. It is nice for us parents to have an excuse to get involved, as it gives us an opportunity to point out connections between the material and other interests.
