Here's a question that I don't recall ever getting answered by people in favor of teaching intelligent design: what exactly would you teach? The whole idea can be stated in, like, one minute flat, and there's no physical evidence, scientific tests, or anything that can be examined to expand upon the idea. As far as I can tell, all you could do is say "Intelligent design is another theory, and it says that God created the universe and everything in it" and then you'd be done, end of lesson.
Um, no. Intelligent design is about probabilities. It says nothing about who created the universe. It does not state that God created the universe. It could be an alien race as far as intelligent design is concerned.