[Kevin]

And if Facebook isn't blocked int he school, then the publication of the comment does actually extend into the schoolhouse and could arguably affect discipline within the school.

The First Amendment isn't unlimited. This isn't defamatory speech though. It's just simple invective. That said, I think whether it is occurring in the school and whether it affects discipline in the school is determinative here. Aside from that, nothing absolutely groundbreaking about this at all. Would the Principal like his life better right now had he left well enough alone? Heck yah.. but the school has a fighting chance if this doesn't settle.