"But should the possibility of God be banned from scientific discussion?"
It's not a scientific question. It's a theological/philosophical one.
"I'll readily grant you that science can't determine whether or not God exists, so that issue has no reference point for a scientific investigation, but I don't see any problem whatsoever if, for example, a single day was spent in science class discussing whether or not a deity or other intelligence authored the order we see in the universe, or created life here."
If, as you just said, the question of whether there is or isn't a God is not capable of being determined by science, why would you want it discussed in a science classroom?
I wouldn't mind seeing God discussed in science class because it could well be true that God is responsible for life existing on earth, for order existing in the universe, etc.
If the possibility of God is not a scientific question, then why does science declare God is outside of its purview? Is it qualified to make such an assertion? How so?