How my 'public' school violated my rights concerning Facebook

No, I don't think they did that to you. First, the standard disclaimer... I am no lawyer.... yadda, yadda, yadda.

We need to put this in context. The 1st amendment exist with the purpose of protecting citizens who express opinions that contradict the official line of the government. It is, above all, a political device.

I am not familiar with the burning flag case you mention, but I'd bet pennies to dollars that the incident happened within the context of someone protesting against some form of American policy (maybe foreign policies I'd guess). It is not the random act that the first amendment protect, but the significance behind that act, within the context of some citizen expressing disagreement with the actions taken by elected government officials.

Your case is not so. It can be a number of things, but it is not a violation to your political right to express dissent.

On the other hand, you need to learn the difference between "what you think the law says" and "what interpretation of the law will held in court"; and then compare it with "what the cost (in money, time and personal distress) will be to defend such and such particular interpretation in court". The school official was right. Maybe you are theoretically entitled to publish those photos, but eventually you would walk into someone that would get pissed off. Is it really worth it to pick a fight with such person?

And, maybe for you it would be... if you where somehow monetizing the page. But the school has nothing to win and everything to loose in that situation, so it is natural for them to align with that hypothetical pissed-off parent.