Thanks everyone, good suggestions as always.

To answer some of the questions:
We are boarding and day student
I am trying to cover all bases, so both shelter in place and bug out
Classroom doors do not lock from the inside - I will need to look at that.

This is not going to be an overnight fix, unfortunately. My first chore is finding out who has what kind of experience that can be utilized in an emergency. Then I'll start collecting gear. Of course there's no budget for this so I'll need to do some shopping around as well.