religious theory isn't always apart from evolution. I know that some christians believe in both creationism and evolution, in the sense that we weren't granted our "human gifts" until we evolved into humans.
So teaching evolution does not go against religion in most cases.
Of course evolution should be thought in schools why it should not be? Hell it is already thought here and its already proven to exists in the micro organisms? however Theory of our origins shouldn't be imposed but definitely researched upon its just a theory.
How can evolution NOT be taught in schools is the better question. Evolution is a main concept in biology and anthropology and without it, these subjects really make no sense. Also, regardless of beliefs, students should be presented with information that is backed up by EVIDENCE. Which is why I'm not opposed to Christianity also be taught in schools because there are aspects of Christianity that have historical evidence.