It was Leftist speech that SCOTUS defended in this case but it offers a very useful precedent for political speech at schools and colleges generally:
"Putting its recent ruling on student speech into practice, the Supreme Court on Friday rejected a school district's appeal of a ruling that it violated a student's rights by censoring his anti-Bush T-shirt.
A seventh-grader from Vermont was suspended for wearing a shirt that bore images of cocaine and a martini glass-but also had messages calling President Bush a lying drunk driver who abused cocaine and marijuana, and the "chicken-hawk-in-chief" who was engaged in a "world domination tour."
Williamstown Middle School Principal Kathleen Morris-Kortz said the images violated the school dress code, which prohibits clothing that promotes the use of drugs or alcohol.
An appeals court said the school had no right to censor any part of the shirt. On Monday, the court said schools could regulate student expression if it advocated illegal drug use. Justice Samuel Alito cautioned that schools could not censor political speech.
Source
Drug advocacy is not political? So they tell us. I know many libertarians and Leftists who would violently disagree. But we must be thankful for small mercies. The rules now appear to be that non-drug political speech is protected.
More detail here. Apparently it is OK to mention illegal drugs (cocaine in this case) if you depict the President as using them! That is not encouragement of drug use, apparently. I guess that the Bush-haters would see it that way so maybe it makes some slight sense.