Commenter Jennifer's anecdote from the trenches of public school teaching in the thread for this post is worth repeating:
I taught "Merchant of Venice" to seniors one year; in it there's a line where one character is insulting another, by saying something along the lines of "He damns the ears of all who hear him, by calling him 'fool.'" One of the kids asked me what that meant, so I explained that one of the lesser-known verses of the Book of Matthew has Jesus saying that anyone who calls another a fool will be damned. (I recited chapter and verse, though I can't remember it now.) I went on to talk about the very funny use Voltaire made of that in his essay "The Jesuit Berthier" (an angel tells a priest to stop giving his stupid, boring sermons, because instead of winning souls for God he's endangering the souls of all who hear him, because they all call him a fool), and explained also that this is why cartoony villians in movies developed the habit of using "Fool!" as their default insult; for people familiar with the Bible, the fact that the villian always says "Fool!" is just one more proof that this is an evil, evil dude.
"So anyway," I said to the class, "back in Shakespeare's day, when people were far more familiar with the Bible than they are now, instead of insulting someone by saying 'You are a fool,' you'd say 'You are a--well, I can't SAY what you are because then I'd go to hell.' That's what he's doing in the play."
Next day I get called into the principal's office; some parents were FURIOUS that I had told their kids that Jesus said anyone who says 'fool,' will go to Hell.
"But he did," I pointed out.
"It doesn't matter, Jennifer. You can't insult kids' religions."
"Well, the kid asked me what that line from the play meant! What was I supposed to do?"
"Just tell him you don't know."
Probably not really a public/private thing—I can imagine this happening about as easily at a private school. Just an appalling illustration of the mindset that subordinates the pedagogical mission to the principle of never risking offense to anyone.