"She told them magic does not exist. There is no such thing as magic anything."
Montville Schools superintendent Rene Rovtar said she was "troubled" and "disheartened" by the incident.
"The childhood wonder associated with all holidays and traditions is something I personally hold near and dear in my own heart," Rovtar said.
Cedar Hill School principal Michael Raj sent a letter to parents advising them he had spoken to the teacher about her "poor judgment".
"I am sending this letter so that you are aware of the situation and if the conversation comes up at home over the next few days you can take appropriate steps to maintain the childhood innocence of the holiday season."
He then apologised to parents, saying as a parent himself, he is "truly aware of the sensitive nature" of the announcement.
School district officials refuse to comment on whether the teacher is still working in the district.