Excluding the Supernatural

Abstract

Occasionally, you hear someone claiming that creationism should not be taught in schools, especially not as a competing hypothesis to evolution, because creationism is a priori and automatically excluded from scientific consideration, in that it invokes the "supernatural". So... is the idea here, that creationism could be true, but even if it were true, you wouldn't be allowed to teach it in science class, because science is only about "natural" things?