Creationism should not be taught as science in the public schools. It would be appropriate to teach creationism in any class about religion (like a world religions class), but it should not be taught as part of a science curriculum.
The reason for this is that creationism is not accepted by the vast majority of experts in the field. Public schools should teach only those things that are accepted by experts. Creationism does not meet this requirement. There are some scientists who do believe in it, but they make up a very small minority. Public school science classes should teach what is accepted by the scientific community, not what is believed by religious groups.