If you want an objective measure of a school's ability to serve GT students in CA, I'd browse this list of National Merit Semifinalists for the schools in LA area and then look up the number of students in the senior class and calculate the percentage earning National Merit. If a Public School is top on the list, then you need to look at the feeder middle and elementary schools. By definition, NM winners are in the 99.5 of their class.

http://www.ibabuzz.com/education/wp-content/uploads/files/2009/09/natlmeritsemifinalists.pdf