[thecavemaster]

I would say that, given the Nazarene's instruction, a teacher or student can pray any day, all day, any time, anywhere in any school. The "private closet not to be seen of men" thing being applied, that means: put head down on desk, go to restroom stall, put hands over face... or, simply, reflect and meditate in one's own head, with one's thoughts open to the heavens for give and take. I'm pretty sure the "still, small voice" won't disturb anyone else around you.