No for many "Santa" is the epitome of giving. Not consumerism.
It depends entirely on how you view it.
I know people who volunteer at soup kitchens on the holiday - that is their Christmas every year. Should their 1st graders be made to disbelieve by a substitute teacher?
No. That was not her job.
No belief in the make believe is part of most childhoods. "Magical Thinking" is Normal.
When that belief is suspended depends very much on parental decisions.
This was not up to a school teacher. A substitute one in fact?
It was not part of her job description in any fashion.
Most of what we celebrate goes far past paganism into even further back solstice celebrations to encourage the return of the Sun from the dark realm.
I mean gees - kind of heavy for a 1st grader?
Absolutely rampant consumerism is terrible for adults. However for a child? Not so much.
Let kids be kids.
Saying that there is no Santa, no Easter Bunny, etc., is not a decision for that sub teacher to make. It's up to the parents to decide when the child is ready to be told. Yes, strictly speaking, it's perpetuating a myth, but it's up to the family to decide how to deal with that myth. This teacher made him/herself the judge of what is right and wrong ("It's wrong for these children to believe in Santa" ), and that's not a choice that she/he should make.
It's kind of like how parents deal with teaching their kids about sex. I may disagree with what a parent chooses to do or say on this subject, I might disagree with them in a discussion that the child was privy to, but I would not independently seek the child out to "set them straight." It wouldn't be my place to do this, nor is it my place to tell anyone's child (unless they are 15 or something) that there is no Santa.
Also, since this person is a substitute teacher, strictly speaking, s/he is not being deprived of a livelihood. Who knows whether this person was teaching full- or part-time? This individual may not have been totally dependent on that income, and there are other districts that need substitute teachers. And hopefully this person will now think twice before debunking a dearly-held childhood belief.
She stepped outside of her remit....and she sounds a bit like a Spoilsport to me. I believe it is pretty harmless for children to believe in Santa and the Tooth Fairy, they grow up and out of these childish notions in the natural course of things anyway. If only they grew out of their belief in Jesus and God as easily.....now if some brave teachers want to take that mythology on, then they would have my wholehearted support.