Something must be taught that explains animal and human origins from a scientific point of view. Intelligent design and creationism both purport some higher power is behind humanity. Anthropology and biology must be based on science and hard facts. That doesn't leave room for God or any spirituality to explain how life started and evolved on Earth. If you want answers as to how, that's science. If you want answers as to why, consult your spiritual leader.
Through out history people have placed things they can not explain to the supernatural. Evolution however is scientific and proves how living things came about and formed. That is why evolution should be allowed to be taught, but creationism should not. Creationism is only peoples faith, which is all different.
I would have no problem with schools teaching creationism as part of a course in literature. But it doesn't belong in a science class. Evolution does belong in a science class, because there's an overwhelming amount of evidence obtained through impartial research that it happened. Creationism's core message is "and then magic happened!"
Personally, I believe evolution should be taught in public schools because it is the most viable theory we have that explains our existence. Creationism is something solely believe because the Bible says for, which is quite enough for me or the vast majority of the world. If it suits religious people to use the excuse, because of the separation of church and state, then so be it.
Creationism is not taught in school as it has been deemed pseudo science. I gather this is a question regarding the American schooling system as it talks about separation of church and state. Good this really, that schools are not legally allowed to teach lies to students. After all what kind of relationship are you cultivating when you are lying to someone.
Public schools should not be teaching evolution in place of creationism, but should offer both perspectives. Enough people believe in one or the other (or some combination of both) that it is valid to present both beliefs and let the students apply their own knowledge to make their own decision on what they believe. Schools should not be teaching one or the ohter as fact, but present both as viable theories.