This is also, partially, in reference to the several other folks who quoted me.
I have no problem using religion as an example. Nor do I have a problem with teaching what religion is. I'm currently a substitute teacher, but what I want to teach is history. There's no possible way to do that without understanding religion as that factors into the entire history of mankind in one flavor or another. I got caught up in the doctrine part. I think there's a pretty big difference in teaching kids that a Christian generally believes x, y, and z and going into the dogma of the religion.