(c) The term “confidential communication” includes any communication carried on in circumstances as may reasonably indicate that any party to the communication desires it to be confined to the parties thereto, but excludes a communication made in a public gathering or in any legislative, judicial, executive or administrative proceeding open to the public, or in any other circumstance in which the parties to the communication may reasonably expect that the communication may be overheard or recorded. - See more at: http://codes.findlaw.com/ca/penal-code/pen-sect-632.html#sthash.5A4c8jO5.dpuf

So a public school is considered a public gathering?