The root cause of the collapse in math education in California is one bad researcher's work, combined with politics.
Briefly, a Stanford-affiliated "researcher" named Jo Boaler produced two deeply underpowered studies claiming to show that putting all students in the same grade-level math course led to better outcomes for everyone — even the kids that would've normally been tracked into advanced math. But she only tested results on grade-level math — of course the would-be advanced kids did better on "grade level" math if they've taken it recently. The loss is the advanced math they didn't take.
Here's an article:
https://stanfordreview.org/jo-boaler-and-the-woke-math-death...
I fought with my son's middle school administration about this precise issue. It is the stated policy of CA's state level education department to de-emphasize advanced math and tracking, in favor of these deeply suspect ideas. I'm pretty progressive in general, but this is braindead stupid, alarming, and self-defeating. (If you care about equity, you NEED to have options in the public school for the underprivileged gifted kids! the rich kids have lots of options and will be fine.)
It's deeply depressing, but education has long been a weak spot for California; since Prop 13 in the 1970s, California has been 49th or 50th in per-pupil funding for public education (excluding college, I think). But to compound that with this wrongheaded, moronic, politically suspect and quantitatively incorrect policy is... infuriating.