When I put that question to Paula Fass, a historian at UC Berkeley and the author of The End of American Childhood: A History of Parenting From Life on the Frontier to the Managed Child, she brought up two eras as analogues. The first was the early stages of the Cold War—the 1950s in particular—when fears of nuclear bombs had schoolchildren across the country doing duck-and-cover drills underneath their desk.

Surveys of children who grew up in this era indicate that 60 percent of them reported having had nightmares about atomic bombs. Fass herself lived through nuclear-prep drills, and while she said that they weren’t all that scary for her—they became rote, like reciting the Pledge of Allegiance—she recalled one night during the Cuban missile crisis, in 1962, as particularly anxiety-inducing for a high schooler: “I remember going out that evening on a date, and as we parted ways on the New York subway, we said to each other, ‘We may never see each other again.’”

The second period when families felt a looming threat, Fass said, was the 1980s and ’90s, when there was a “pervasive fear” of kidnapping among parents and kids alike. They received constant reminders of children who had disappeared—their faces were on TV, billboards, mailed flyers, and milk cartons. Some of the missing were from small towns, and others were from big cities. “It didn’t seem that there were any protected places,” Fass told me.

Fass, who wrote a book about child abductions called Kidnapped in 1997, said she heard of police officers showing up at schools in a push to record kids’ fingerprints, “not because they would be able to locate them that way, but because if they located their bodies, they’d be able to identify them.” All this scared children: A 1987 poll found that their most common fear was being kidnapped.

These widespread panics took a psychological toll—were they proportional to the actual risk? In the case of the Cold War, it’s hard to say, because while the United States never experienced a nuclear attack, there was a real sense that one might occur. (And some evidence indicates that ducking and covering might actually have been a wise tactic for these kids, at least compared with doing nothing at all.) The kidnapping panic, meanwhile, seems overblown in retrospect. In 1997, for instance, only about 100 of the 71 million children in America were abducted by strangers.

This isn’t to say that kidnappings and nuclear blasts wouldn’t be devastating—just that they are exceedingly unlikely. Shootings, too, seem to fall under this category of threat. Starting with Columbine, according to the Post, school shootings have claimed some 150 lives, including both children and adults. That’s 150 too many, but as a percentage of all the students and teachers who have been in a school in the past 20 years, it’s quite small. (The number of children estimated to have experienced gun violence at school during that period—roughly 230,000—is also much too high, but still a tiny minority of the tens of millions of American children in school at any given time.) Lockdown drills are schools’ attempt to protect kids from an unpredictable threat. But, across the country, children are being trained to anticipate an outcome that is both terrifying and extremely unlikely to happen to them.