Creationism is considered by most biologists to be a pure fabrication. There is insurmountable geological, physical, logical, biological, etc. evidence against claims that the Earth was created 6,000 years ago and that all existence it the result of the work of on omnipotent being.
Although many argue that children should be taught to see both sides of the argument, creationism has no scientific basis. The only evidence for this "theory" lies in the bible. Being a religious text, the bible should not be consulted for factual information, as well as the fact that it is generally considered to be open to interpretation.
Furthermore, as mentioned earlier, it's "factual" basis lies in the bible, a religious text. Under the 1st Amendment, the government should not endorse its establishment.