Unlike evolution, why isn't creationism part of biology and geology?

As Creationism has no scientific basis or actual physical evidence to support it, it can only be considered a belief. There is nothing biological or geological that proves the theory of Creationism, so therefore the two are unrelated, and it would be very difficult for a Biology/Geology teacher to teach their students the Biological and Geological aspects of Creationism when it has none.