Lockout, as in "the schools are on lockout due to an armed gunman in the vicinity." That's the way the news was phrasing the story yesterday.
I could see "lockdown", or "lock-in" (the kids are locked in until everything is clear, but "lockout"? That reads to me as if the kids are locked out of the buildings.
Maybe it's just counterintuitive to me. But I'd also like the word to go away because it's beyond ridiculous that the concept is even something I should have to worry about as a parent of students, a parent of a teacher's aide and of a school staff member, and a wife of a teacher/sometimes volunteer first responder.