Yes they are. Knives were originally governed under California Penal Code 653(k), but this has been renumbered to sections 16100 – 17360. These sections provide definitions of all types of knives, dirks, daggers and the like. Penal Code Section 626.10 is what specifically prohibits knives in and on schools grounds and buildings.
One of the best write ups on the issue that I have seen can be found here http://zknives.com/knives/articles/law/caknifelaws.shtml
As always, consult an attorney if you are considering carrying knives. If you have someone carrying a knife on a school campus and you did not instruct them to bring it, then call your local law enforcement officer immediately.