I suspect CA’s child poverty rate has a lot to do with young, poor immigrants in the state. If that’s the case, then California’s commitment to educating the poor – thus making it a really attractive place for the poor who have or expect to have children, and who want their children to be better off – may very well serve to increase, rather than decrease, its child poverty rate.
All of which goes to show why one shouldn’t place undue weight on any simple policy measure like “child poverty rate.”