I can't speak for anyone else on this thread, but what I'm angry about is that the teacher committed an act that she had to have known would be emotionally upsetting to at least some of the young children she was teaching, and went ahead and did it anyway. She is quite free to believe as she wishes, and live her own life however she desires. But when she sends a bunch of six-year-old kids home crying to their parents and then tries to play a "freedom of expression" card to save herself when she gets called on the carpet for it, there's a problem.
I wonder what a good decent Jewish person would do in the same situation. Since they obviously don't celebrate Christmas, how would they handle it. I think most would handle the situation differently. I think most would probably opt out of reading the whole thing, and skip the whole situation.