I gave Standard's Based Assessment a whirl in Algebra II for a semester. The full depth of my experience is shared on its own page. Overall, it has a lot of potential. It moves us from lectures driven by a textbook towards the type of class I loved the most in college where the professor's knowledge of the subject was so great that his/her insights were worth way more than the $200 book.
I may attempt to adapt it to Pre-Cal.