California has plenty of amazing public schools. But California is also highly segregated by both income and ethnicity. Fremont High School, for example, rivals some of the most expensive private schools nationally in terms of achievement, but it's a majority Asian school, especially South Asian, many of whom are middle- and upper middle-class (notwithstanding that by Bay Area standards the Fremont area is considered "working" class. You can find schools like Fremont all over California, but especially in the Bay Area, coastal Central California, and many places in Southern California.

OTOH, just a few miles from some of the best public schools in the country you can also find some of the worst. While California is segregated, most Californians nonetheless live in relative close proximity to people living in vastly different circumstances, so disparities are very evident.