That's because the students are shut down if they attempt to discuss God OR Creation. If you had kids and/or were involved in their studies you would know that.
I have had kids, I was involved in their studies. But over and above that, I have taught science, including evolution, and also talked with students who brought up God and creation in class--whether that class was evolution, math, or P.E. And, yes, God pops up all over school--not as a rule, but it's not ruled out.
Here's the deal. A teacher has a lesson plan that is used to get students from Point A to Point B in all five or six periods. If one period has a student that wants to solely discuss God, then the entire class is a day behind in the science curriculum. How I have always handled it is how I handle anything that deviates from the lesson plan: Briefly address any comment or question, and then get back to the lesson plan, noting that anyone who wanted to talk to me further could see me after class, before or after school, during lunch or their homeroom class.
Creationism is not science, and therefore it is never going to be found in a science lesson plan. Likewise, philosophy is not science, and it is not going to be found on a science lesson plan. This does not mean science teachers discourage students from studying theology or philosophy. It simply means they won't be studying them in science, any more than a science teacher will have students study a play or play softball during his/her class.