Some high schools around here do "regular lockdown drills".. but they are unannounced to the students.
The faculty/staff are somewhat aware (like they know what day/ but time unknown)
I learned this when my daughter was at a preschool housed in a high school . Right before preschool started, we got frantic calls from the teacher in charge -- saying the kids are on a lockdown drill, don't bring the younger ones.
One time during lockdown drill, they brought the drug sniffing dogs, and found some pot in lockers.