I think both the Principal and Teacher were out of line. They should have just stated that different people have different beliefs that are neither right or wrong and that school is not the place to discuss this. IMO
I feel it is inappropriate to express any truth in religion in schools. It's a hard line but if we can agree religion is simply not based in any reality at all, why would you support its teaching or being said to be true?
People believe the moon landing was fake but we don't teach it to kids in science class.
As far as the teachers go, i would talk to the principal about any concerns you have.
I think that you have the right to be upset. Neither the teacher nor the principal should have interjected their personal opinion on the existence of god. Although older children may be able to distinguish between fact and opinion, I'm just not sure that young children would be able to reconcile the idea that the teacher and principal are delivering information that is potentially untrue. Besides, isn't that idea completely counterproductive to the intent of elementary education? Children are sent to school with the intent of being educated by an adult who possesses superior knowledge. I think that it sets a bad precedent for children that young to question information delivered by their teachers. Neither principal nor teacher should opine on matters that are essentially up for debate as young children are generally not equipped to understand the associated debate.
But I will concede that I don't have children. Maybe my experience with young children is completely off and they are, in fact, able to easily distinguish between facts and opinions offered by authority figures. I just think that the information delivered in elementary school should be restricted to the academic basics of spelling, math, etc.
And as a parent of a 6 year old, I can attest to the fact that they believe most things told to them by their teachers or trusted adults, as you would expect them to. They are spending all day teaching them to read and write and other "facts", why should anything else they tell them be false?
My son believes everything his best friend tells him. He's 6!! LOL
I want my kids to think for themselves, so I always ask them what they think before answering a question. I want them to use their critical thinking skills, but at this age, they are too impressionable. My son doesn't question Santa or the Tooth Fairy, so why should he question God existence?