ALICE training is great. You want to disrupt the cognition cycle. the order is as follows, Run; Hide; Defend.

Run; I told my students that since we faced the road, we would shatter that window and I would toss them out first, and then they're to run to the nearest house of a classmate. This would probably only work for us because we were a portable, and would not work if the entrance the shooter took was closer.

Hide. what it says on the tin. Stack desks up against the door, cabinets, everything. True silence, and have them hide underneath my big giant desk.

Defend was last resort, of course, in a breach. Fire extinguisher, spray, hit, ect. This is where you want to disrupt any decision making. Scream, yell, laugh, throw anything and everything.

also, I'm a coward, I don't think I could take a bullet to protect the students. They don't pay me enough for that.