What an interesting thread!
I must admit, I am confused by some of the arguments being offered here.
On the one hand, many people are saying that "Santa Claus" is a myth (like The Illiad), or a fantasy story and thus there is no harm in teaching about him. After all, the Iliad is taught in school, as are fantasy tales like "The Lord of the Rings".
However, children don't believe those things are true. If something is a myth, children are told that it is a myth and when I was a child, it was stressed that myths are not true.
On the other hand, much of the anger directed at this teacher seems to be precisely because she taught Santa as a myth, a fantasy tale, and not the truth.
If Santa is a myth, then what is wrong with calling him that?
Do people teach their children that Frodo and Sam are real people?
See my post #536.
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.