Spewing expletives all day long without consequence is a right, guaranteed by the first amendment. If the school system doesn't like it, it's free to relocate to a country where free speech laws don't apply.
I still don't understand why this went all the way to the supreme court. It's such a clear-cut case of free speech. Some school admin's reading comprehension must be really poor if they couldn't make sense of the first sentence of the constitution.