The JW student has to leave the room or they can't discuss it. Might not be a shared belief but certainly for this pupil they are making an exception. The pupil has elected to take RS too so must have known these things would be covered as would her parents. Like I said, more of an issue with the school and likely their parents not communicating properly. Does make her stand out to other kids though, can't be healthy for her.
Sorry but I simply don't believe that, as you're stating it.
For one, there is no problem with JWs discussing Christmas. It's actually a very common subject for discussion, because people have heard about it and often ask JWs why they don't celebrate. Another one is why don't they have blood transfusions.
Can you imagine having those beliefs and then refusing to talk about them? Would be silly. And I've talked with many JWs about those exact subjects.
For two, the school would be mad to restrict the curriculum based on the *wishes* of one pupil. The other parents could rightly object and demand the full curriculum be taught. I know I would.
For three, what exactly does "discussing Christmas" actually mean? We all know what Christmas is, and being "not allowed to discuss Christmas"... that would be
extremely strange and quite a little vague, too. Can't talk about presents? Christmas trees? Turkey dinners? What, exactly, can't they talk about?
I'm sorry but your story just doesn't add up.