Basically once an intruder is reported, an announcement is made that all the staff, faculty and students know means, find a place to hide. Teachers immediately go to the classroom door and get any child in the hallway, into their classroom. We than lock the door from the inside, and have the students get on the floor near an interior wall, (not visable from the door window)We turn out the lights and the kids sit silently.
That's good.
I forgot one thing, we keep the window shades up, so if need be law enforcement can see what is going on in the classroom.
Fortunately, my kids are now out of school. I know when I volunteered (2 years ago) there were no drills at our school. Administrations better wake up!