A new TV ad sponsored by the group Sandy Hook Promise depicts school shootings as a quotidian reality for children and teenagers in the United States, an ever-present threat that must be addressed through careful preparation and constant vigilance. The spot is emotionally compelling but highly misleading given the rarity of such incidents, inflating a tiny risk in a way that fosters unjustified anxiety, which tends to result in misguided policies and wasted resources.

The ad begins with a student at his locker, bragging about the backpack his mother bought him for the new school year. It continues with other students showing off their new purchases, which they use to deal with a mass shooter who is attacking their school: Sneakers come in handy as a student runs from the sound of gunfire, a jacket is used to tie closed a pair of doors to keep the shooter at bay, a skateboard is used to break a window so students can escape, a pair of scissors becomes a defensive weapon, a knee sock becomes a tourniquet for a wounded girl, and a crying girl hiding in a bathroom uses her new cellphone to text what may be her last words to her mother. "It's back to school time," says the closing caption, "and you know what that means. School shootings are preventable when you know the signs."

School shootings, like airplane crashes and terrorist attacks, are dramatic and horrifying events that get a lot of attention precisely because they are unusual. FactCheck.org counted 64 deaths from school shootings between the Sandy Hook massacre in December 2012 and the end of 2018. That number includes "students who died after being shot on school grounds, during school hours or after being shot on college campuses—or at student housing—where they were enrolled for classes." The total amounts to about 11 deaths per year, including college students as well as minors.

School shooting fatalities represent an infinitesimal share of all firearm-related deaths among children and teenagers, which mostly involve homicides committed away from school and suicides. Car crashes killed more than 4,000 people 19 or younger in 2017, while 1,430 died from suffocation, nearly 1,000 drowned, a similar number succumbed to drug poisoning, and 340 died from fire or burns. In other words, children and teenagers are about 370 times as likely to die in traffic accidents and about 90 times as likely to die from drowning as they are to be killed in a school shooting. Lightning strikes kill more than twice as many people each year.

Fatalities aside, school shootings are extremely rare events. From April 1999 through May 2019, according to a Guns & America tally, there were 68 K–12 school shootings in the United States, including every instance where "a gun is brandished, is fired, or a bullet hits school property for any reason, regardless of the number of victims, time of day, or day of week." Even using that broad definition, there were about three school shootings a year. In 2018, the year with the most gun-related incidents at K–12 schools during this period, there were nine.

When you consider that there are about 133,000 K–12 schools in the United States, the risk that one of them will be threatened by a gunman in any given year is somewhere between 0.002 percent (using the 20-year average) and 0.007 percent (based on the 2018 total). The risk over the course of 13 years, from kindergarten through 12th grade, is between 0.03 percent and 0.09 percent. Yet Sandy Hook Promise is telling us that the risk of a school shooting is something that every child and parent needs to worry about, a danger that requires new "programs and practices that protect children from gun violence."

The organization presents its agenda as utterly unexceptionable. "By uniting people of all beliefs and backgrounds who value the protection of children to take meaningful actions in their homes and communities," it says, "we will prevent gun violence and stop the tragic loss of life." That certainly sounds noncontroversial, as does Sandy Hook Promise's claim that "school shootings are preventable when you know the signs."

But is that true? In retrospect, many school shooters showed "red flags," and in some cases (such as the 2018 shooting in Parkland, Florida) better attention to those signs might well have prevented their crimes. At the same time, almost none of the people who display what others interpret as red flags are actually bent on mass murder, so false positives will swamp true positives. That reality creates a risk not only of wasting law enforcement resources but of maligning and humiliating a lot of innocent people.

Or worse. Sandy Hook Promise seems to favor what it describes as "Extreme Risk Laws," colloquially known as red flag laws, which strip people of their Second Amendment rights without due process. Based on the vanishingly small risk of school shootings, the organization is advocating a policy that takes away people's constitutional rights when they are deemed a threat to themselves or others. The standards for issuing gun confiscation orders can be as weak as showing, by "a preponderance of the evidence," that the respondent poses a "risk of danger," whatever that means. And whatever the standard, judges have strong incentives to err on the side of issuing orders, lest they be blamed when something terrible happens.

Judging from the experience in Connecticut and Indiana, the two states with the oldest red flag laws, most gun confiscation orders have nothing to do with threats of violence, let alone plans for a school shooting. Instead they are aimed at people who are deemed to be suicidal. Even when the justification is that the respondent poses a threat to others, the evidence can be shockingly thin. In practice, the hunt for red flags can mean that someone loses his Second Amendment rights for a year or more because of a misunderstood (or misrepresented) conversation or because he said something offensive or controversial on social media.

Inflating the risk of school shootings also can lead to irrational school policies that invade privacy and undermine civil liberties. Last year, the Plano Independent School District, which runs the middle school my youngest daughter attends in Dallas, announced a new policy authorizing "random, suspicion-less metal detector searches" of students in grades 6 through 12. The district planned to use "both walk-through and hand-held metal detectors" on "random groups of students," who would be required to "remove all metallic items from their pockets and person." In addition, "backpacks, bags and personal items capable of concealing a weapon will be opened and inspected for the presence of weapons." Any student "who refuses to comply with the search process will be removed from campus and subject to disciplinary consequences."

According to my daughter, none of this has actually transpired at her school, so the policy may be mainly for show. Even if it were implemented, it would be pure security theater.

It strains credulity to imagine that a program like this would deter someone determined to commit mass murder. As the Texas Association of School Boards notes regarding metal detectors at entrances, "there is no guarantee…that a metal detector will stop a determined individual with a weapon." It cites a 2005 attack in Red Lake, Minnesota, where "a student shot and killed seven people at his high school, including an unarmed security guard who was operating a metal detector at the main entrance." Periodically scanning "random groups" of students would be even less of an obstacle to a mass shooter.

But such security practices do accomplish something. They condition teenagers to surrender their privacy in response to arbitrary edicts from people in authority, based on zero evidence that they pose any kind of threat. Training young people to accept such invasions leaves them ill-prepared for situations in which police overstep their authority. People who are accustomed to being searched for no reason at all are not likely to assert their constitutional rights when a cop asks if he can peruse their cars, homes, or personal belongings.

When Sandy Hook Promise advocates "programs and practices that protect children from gun violence," skeptical readers should fill in the blanks with policies like these, which cast a wide net that catches far more innocent people than would-be killers. Like the similarly minuscule risk of dying in a terrorist attack, the danger of school shootings has been grossly exaggerated to the point that any policy said to address it, no matter how dubious, wasteful, invasive, or unfair, has a decent chance of being adopted.

"We're trying to unite people in the common good of saving kids' lives, as opposed to saying we should ban guns," the chief creative officer at the advertising agency that created the Sandy Hook Promise spot told The New York Times. "It's not about picking a side and defending it."

That is obviously not true. Sandy Hook Promise and its allies have picked a side. It's the one that favors overreacting to an objectively tiny but emotionally resonant danger. It's a side so confident in its own virtue and good sense that it cannot imagine how any decent, reasonable person could disagree.

[This article has been revised to note that the figures for various causes of death include 18- and 19-year-olds as well as minors.]