(What kind of Christian presence have you noticed in schools?)

This is a little outdated, going back to 1999 when I first attended public high school in Texas, but I was very impressed with the public expression of Christianity. Soon I would learn why they call this place the "Bible Belt."
Kids met every morning to pray around the flagpole. There was a Christian Youth Brigade or something to that effect, that met at the school and did charity things and such. The school would announce about their meetings and events during pep rallies.
I even had a couple teachers who refuted what was in our textbooks. They would say such things as, "Now this is what we have to study for the test but we all know it's a bunch of nonsense and remember to read our Bibles."
Things may have changed quite a bit in the last 9 years, but in '99 I was impressed.