lj,
We do more than 2 lockdown drills a year. I teach at-risk kids. Our administrator would say "Lock down, now" on our PA system. We used to have a code for this (like "there's a teacher meeting at 8:30 pm") but that is too confusing. We use a slip of paper under the door - different colors for safe inside or not safe (injured or heaven forbid, with intruder).
I worry the most about student panic and retaliation, especially with my students, who are not rule-followers to start out with - in fact, most are fighters. I have been talking to my students about these events. I can't say that I am entirely happy or entirely unhappy with their attitudes and comments (another subject).
I do feel many would defend me, and to some extent each other, but I also feel many are terribly angry and unpredictable and MANY have access to guns at home. In fact, there are times I think certain parents are more likely candidates to be shooters at our school than students.
Most of my students are not the withdrawn/bullied/isolated/anonymous types sometimes profiled as potential shooters. They're pretty "out there" with their hostilities. Still, no amount of profiling can predict this type of thing. Of course, as we see with the Amish school, it is just as likely a violent intruder is not a student at all.
Eve