Earlier: "... Installing Tor on a school computer, if it's even possible, would almost certainly be in violation of the school's rules and policies regarding computer use..."
Peter Blaise responds:
So go ahead and try it! ;-)
Tell 'em we told you to do it - it's okay.
We're programmers, and we're grown ups.
We be smart. =8^o
Actually, I respectfully decline to act as ad hoc surrogate police for any other party, especially anyone trying to lord it over children. I figure each party can negotiate with each other party without my generalizing advice ... except to say: (a) I don't think judges hold anyone under age to a binding contract, and (b) I don't think a judge inflicts a non-negotiated contract on anyone, and (c) I don't think any judge will uphold any contract without "consideration" between the parties, that is, money change hands.
Ask a lawyer who practices in your jurisdiction.
Fight the Power!