Legal Question in Technology Law in California

The First Amendment provisions for freedom of speech ad press allow you to do almost anything, except for porno for profit, but does not shield you from a civil suit for harming another person or their reputation, etc. So if your posting makes the teacher look evil, extremely stupid, etc., they might be able to successfully sue for defamation of character, but I doubt they would go to the trouble of doing so. The school principal, however, might try to claim what you did was disruptive of class atmosphere. I would suggest you take it down, as you probably did you the teacher's image to draw attention to them for your classmates. The Golden Rule is a very simple test for behavior. Would you want without any question someone to do to you what you did to them?

I pretty much agree with the previous answer. While the First Amendment is quite protective of satire and lampoon, there are limits, and damaging caricature of a person who is not a public figure may step across the boundary of free speech into the area of unfair and excessive intrusion into the subject's privacy rights. The Golden Rule is not a statute, but it is a pretty reasobale measure of fair behavior.