What this story doesn’t mention that it should is this from Editor & Publisher:
California’s education law was one of several so-called “anti-Hazelwood” laws or regulations passed after the Supreme Court’s 1988 ruling that school principals are effectively the publisher of a school paper with the same authority to censor or otherwise limit student journalists’ independence as the publisher of a privately owned newspaper.
California’s Education Code states that “school districts … shall not make or enforce any rule subjecting high school pupils to disciplinary actions solely on the basis of conduct that is speech or other communication that, when engaged in outside of the campus” is protected by the First Amendment and California’s state constitutional guarantees of free speech.