If you present creation mythology as mythology, there's no problem. Where
the problem comes in is when creationism is presented as a valid scientific
theory. Off the top of my head, I can think of at least three problems:
- Creationism is simply incorrect. There is about as much doubt that
evolution is correct, as there is doubt that the earth revolves around the
sun.
- Creationism is not a theory, or even a hypothesis, it's a conjecture.
To qualify as a theory or hypothesis, a proposition must be testable and
falsifiable. Teaching kids that creationism is a scientific theory
misleads them about the scientific method, and how science works.
- In science, there is no room for "belief" or "opinion". Evidence is
gathered and coldly analyzed, and the results are accepted. Again, to
teach otherwise is to give misinformation about how science works.