You can teach religion in History, Religion or Philosophy courses but not in the Science class. Different subjects. Religion is not science.
It is like teaching Arts in Math.
Probably my most productive 15 minutes in science class was the one time when the teacher (the good one I mentioned) talked about religion. He was probably among the top 10 science teachers in the state I would guess so the example is perhaps a little bit skewed.
On the first day, he described why he was not going to be talking about religion or the bible. In order to do this, he started out be describing the basic fundamentals of hypothesis generation and testing so that he could describe the incompatibility and thus the reason for his stance. He stressed that this did not mean that there was anything wrong about the bible or religion, just that it was not compatible with the philosophy of the scientific method in his opinion and in his training.
One other time this teacher mentioned the bible, or at least the age of the earth. This was in the context of a discussion of carbon-14 decay rates. He mentioned that it _could_ be that the decay rate had changed, then the theory of carbon dating could be wrong. I only remember this (35 years later) because if the insert associated with biblical concepts. So, I don't see why it is necessarily bad to have religion and science co-mingled to some extent. Fact is, these things are co-mingled in real life in our society so it seems fine to me if kids get used to it.
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As for teaching 'Arts in Math', I only remember the 'golden rectangle' at all because of the cross-pollination that some teacher somewhere introduced between the two subjects. I don't remember the details, but I could easily look them up...and only because someone had 'incorrectly' taught one or the other of the subjects.
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I am kind of embarrassed for 'my group' (atheists with a scientific bent) that they seem so threatened and butt-hurt by religion. It is absolutely the case that people should not be discriminated against for their basic beliefs, but that cuts both ways and I see 'my side' as being more of the guilty party at this point in time. I personally am not threatened by religion, but I'll throw in the caveat that I did not feel this confidence until relatively recently, and also that I've got my eye on religious intolerance from the devout side due to the long and sordid history of said.