I've learned over the years that what it says over the door of a school and what goes on inside the classroom are too different things.
Grinity
At my high school, the senior class had traditionally been permitted to paint their class motto above the entry door. To avoid the discrepancy you noted, our class chose a literary quotation as our class motto: "Abandon Hope All Ye Who Enter Here" - Dante Alighieri,
InfernoThere was a HUGE ruckus about whether we should be permitted to put this up.
We were directed to put forth a substitute motto, which we did: "During times of universal deceit, telling the truth becomes a revolutionary act." - George Orwell
Sadly, the school decided that what would go over the door was nothing.