A.F.
I LOVE the advice you have recieved. Absolutely go with your gut! I remember my kindergarten teacher....she was beautiful and so sweet when parents were around, but in the classroom she was HATEFUL. She was angry and degrading to all of us.
GOOD FOR YOU for saying that even though you don't like confrontation that you will do what you have to do. You are your childs BEST advocate.
As far as this being a Christian school, I would detail that to the principle....that you chose that particular school because of the values and that you expected that your child would be in a kind, welcoming, and encouraging environment and that you are greatly disappointed in their standards for teachers. I would say that regardless of the religious affiliation of a school.
Be strong!