Some realistic advice:

http://bethstill.edublogs.org/2012/12/14/preparing-for-the-worst-case-scenario/

The list of survival stuff is short and easy to store in a tote back in whatever corner we're hiding the kids in according to our safety plan. We could add in a list of students, those red/green cards, whatever.

My classroom is across from the office and main door. Let's just say that I'm a bit jumpy about that.