Ryan Marino, an emergency-medicine physician at the University of Pittsburgh, recalled that his school had adopted the drills during that period, after a student was found to have a “death list” and access to guns. He told me the drills didn’t seem real until he was 12, and a fellow student coughed during one of the drills. “The teacher told us that if this had been real, we would all be dead.”

“That single experience shaped my childhood,” Marino said. “Having to practice and prepare for a peer coming to my school and shooting at me and my friends was something that really changed the overall atmosphere. Looking back, it was a major shift in how the world felt.”

In the two weeks since the shooting at a high school in Parkland, Florida, new and renewed calls for such drills raise the question of whether they do any good—and if they might be doing harm.

The day after the event, Susan Hennessey, the executive editor of Lawfare, tweeted: “Feeling mildly nauseous reading a note from my kid’s preschool about implementing active-shooter drills.”

Brian Leff, a writer in Los Angeles, told me his fifth-grade daughter’s principal just announced the school is contemplating a surprise lockdown drill. “Now my daughter can’t stop thinking about when it’s going to happen and how she’ll know if it’s ‘real’ or not.”

The writer Allison Gibson says that at her 4-year-old son’s preschool, they’re called “self-control drills,” because the goal is to get the students very quiet. “The first time he mentioned it, when he was 2, I had to piece together what he was referring to, and it nearly broke me.”

Of course, general lockdown and disaster drills have a long history; a generation of Americans came of age hiding under desks from nuclear bombs. While the idea of such a maneuver protecting a person from a bomb blast or nuclear fallout became fodder for jokes, the drills themselves had insidious effects on kids’ senses of safety. Some teachers reported that students’ artwork changed to feature mushroom clouds and sometimes the child’s own death, bringing a pervasive sense of danger into the places where kids most need to feel safe.

Despite some similarities to natural-disaster and Cold War drills, active-shooter drills also mean exposing kids to the idea that at any point, someone they know may try to kill them.

“It’s good to do emergency drills, but active shooters are not a drill anyone should have to do,” says Meredith Corley, who taught math in Colorado in the aftermath of Columbine. “It re-traumatizes kids who have experienced violence. Getting the kids settled back into the work of learning after lockdown drills is a nightmare. That mind-set has no place in a learning environment.”

“I was slightly too young for bomb drills, but in greater Kansas City, tornado drills were de rigueur,” says Lily Alice, a Midwesterner born in 1965. “We did have tornados now and then. The difference, of course, is that no one stockpiles them to use against other people, and weather forecasts mitigated some fear.”