These drills aren’t limited to the older grades. Around the country, young children are being taught to run in zigzag patterns so as to evade bullets. I’ve heard of kindergartens where words like barricade are added to the vocabulary list, as 5- and 6-year-olds are instructed to stack chairs and desks “like a fort” should they need to keep a gunman at bay. In one Massachusetts kindergarten classroom hangs a poster with lockdown instructions that can be sung to the tune of “Twinkle, Twinkle, Little Star”: Lockdown, Lockdown, Lock the door / Shut the lights off, Say no more. Beside the text are picture cues—a key locking a door; a person holding up a finger to hush the class; a switch being flipped to turn off the lights. The alarm and confusion of younger students is hardly assuaged by the implausible excuses some teachers offer—for instance, that they are practicing what to do if a wild bear enters the classroom, or that they are having an extra-quiet “quiet time.”

In the 2015–16 school year, 95 percent of public schools ran lockdown drills, according to a report by the National Center for Education Statistics. And that’s to say nothing of actual (rather than practice) lockdowns, which a school will implement in the event of a security concern—a threat that very well may turn out to be a hoax, perhaps, or the sound of gunfire in the neighborhood. A recent analysis by The Washington Post found that during the 2017–18 school year, more than 4.1 million students experienced at least one lockdown or lockdown drill, including some 220,000 students in kindergarten or preschool.

In one sense, the impulse driving these preparations is understandable. The prospect of mass murder in a classroom is intolerable, and good-faith proposals for preventing school shootings should be treated with respect. But the current mode of instead preparing kids for such events is likely to be psychologically damaging. See, for instance, the parting letter a 12-year-old boy wrote his parents during a lockdown at a school in Charlotte, North Carolina, following what turned out to be a bogus threat: “I am so sorry for anything I have done, the trouble I have caused,” he scribbled. “Right now I’m scared to death. I need a warm soft hug … I hope that you are going to be okay with me gone.”

As James Hamblin wrote for The Atlantic last February, there is precious little evidence that the current approach is effective:

Studies of whether active-shooter drills actually prevent harm are all but impossible. Case studies are difficult to parse. In Parkland, for example, the site of the recent shooting, Marjory Stoneman Douglas High School, had an active-shooter drill just last month. The suspect had been through such drills, and may have used them to his advantage.*

Moreover, the scale of preparedness efforts is out of proportion to the risk. Deaths from shootings on school grounds remain extremely rare compared with those resulting from accidental injury, which is the leading cause of death for children and teenagers. In 2016, there were 787 accidental deaths (a category that includes fatalities due to drowning, fires, falls, and car crashes) among American children ages 5 to 9—a small number, considering that there are more than 20 million children in this group. Cancer was the next-most-common cause of death, followed by congenital anomalies. Homicide of all types came in fourth. To give these numbers yet more context: The Washington Post has identified fewer than 150 people (children and adults) who have been shot to death in America’s schools since the 1999 shooting at Columbine High School, in Colorado. Not 150 people a year, but 150 in nearly two decades.