The majority is concerned about what it calls "speech that intrudes upon the rights of other students." Judge Kozinski, dissenting, cares about that too:
I ... have sympathy for defendants’ position that students in school are a captive audience and should not be forced to endure speech that they find offensive and demeaning. There is surely something to the notion that a Jewish student might not be able to devote his full attention to school activities if the fellow in the seat next to him is wearing a t-shirt with the message “Hitler Had the Right Idea” in front and “Let’s Finish the Job!” on the back. This t-shirt may well interfere with the educational experience even if the two students never come to blows orHow different is that hypothetical shirt from the one the principal banned? Did the principal disapprove of the shirt because it was disruptive or because it contradicted the school's official message?
even have words about it.