Administrators at Oak Hill High School in Fayette County, W.V., are attuned to potential violence. If a student scrawls a threat on the bathroom wall about shooting someone, which happens in schools on occasion, staff will set up a mobile unit of metal detectors in the school’s yellow-brick entranceway. Since April, though, the metal detectors have been replaced by slimmer-looking scanners that use ultra-low frequency magnetic fields to scan students’ bags and pockets for weapons.

The detectors, sold by a publicly traded security company in Waltham, Mass., called Evolv Technology Holdings, use algorithms that have been trained to identify any kind of gun or knife. If the machines do spot something, they will draw a box around an image of the suspected student and alert school officials. The system costs about $30,000 a year to use, according to Gary Hour, superintendent of the Fayette County school district.

“Students flow straight through it,” he said. “They understand what they have to do.”

In the wake of a steady increase of school shootings in the United States, schools are eager to find ways to better protect their students, even as overall incidents of violence have dropped in the last two decades. But the steps they are taking risk reinforcing an unhealthy culture of surveillance without actually preventing violence.

“Hardening” is the lingo used by lawmakers and educators, who are adding metal detectors, armed security, high metal fences and bulletproof glass. And there is a lot of new technology available to buy: new types of weapons sensors, facial-recognition software and even drones. Schools and colleges in the U.S. spent an estimated $3.1 billion on security products in 2021, compared with $2.7 billion in 2017, according to Omdia, a market-research company.

The result: Schools are morphing into high-security facilities that increasingly resemble prisons.

You can argue that educators don’t have much choice. School shootings are becoming a fact of life and lawmakers have done little to limit access to guns. But among the huge volumes of literature on conducting risk assessments, there is little guidance on how schools should check that new surveillance tools are actually making a difference, researchers have said.

How does Oak Hill High measure the success of its new sensors? A lack of incidents, said Hour. The school’s old metal detector setup was slow and caused long lines that snaked out onto the sidewalks. The lines not only made students late, but also left them vulnerable to a potential attack, Hour said. He added, “I think success comes by making parents feel comfortable.”

There is a trade-off to putting the grown-ups’ minds at ease. A 2016 study by Johns Hopkins University on school safety technology made a startling discovery. There was actually very little evidence that extra cameras and weapons scanners prevented violent events at schools, including mass shootings. There was also little indication that they helped mitigate those events.

A study in 2019 by researchers at New Mexico State University and the University of Toledo reached a similar conclusion. After looking at research and policies between 2000 and 2018, they found no empirical evidence that spending hundreds of millions of dollars on “hardening schools” lowered gun violence.

Both pointed to a common cycle: Horrific incidents spurred new funding with a short spending window, prompting schools to buy technology to show they were “doing something,” according to the Johns Hopkins study.

But there can be unintended consequences to “doing something.” A 2017 study by University of Florida Levin College of Law found that schools with higher proportions of Black students were more likely to rely on intense surveillance measures than did other schools, even when evidence suggested the extra safety concerns were unwarranted. That fuels a broader problem of Black students being punished more harshly than white students for similar offenses.

Increasingly intense surveillance at schools also sends a message to students that they are dangerous and prone to illegal activity, disrupting feelings of trust between students and the school, according to the University of Florida research. Instead of feeling safe, that study showed students felt a heightened sense of danger and disillusionment through constant “passivity and compliance” with the surveillance tech, further eroding students’ Fourth Amendment right to be free from unreasonable searches and seizures.

A day after the Uvalde shooting, Texas Gov. Greg Abbott held a news conference where he recommitted to the state’s “hardening” plans for schools that were passed in 2019, after another school shooting in Houston. Those plans provided $100 million in funding for extra CCTV cameras and bulletproof glass. But Abbott was praising a bill that had ultimately failed to stop the killing of 19 children last month.

Surveillance technology doesn’t address the underlying cause of school shootings, and there is little evidence that it protects children from violence. But it does soothe adults’ nerves. Hour, the Fayette County superintendent, recalled an incident in April when someone posted on Instagram a threat to kill the school principal. News of the threat spread quickly among his students.

Normally that would have prompted about half the school’s kids to stay at home on the request of their parents, he said. Not this time. Parents reminded one another on Facebook that the school had just installed Evolv’s cutting-edge scanners. The next day, nearly all the school’s 3,000 students turned up, according to Hour, who dismissed the notion that the scanners are a form of surveillance. “It was a very normal day.”

It is hard for schools to critically evaluate technology’s impact on well-being — something so difficult to measure outside of academic research — especially when children’s lives appear to be at stake. But the price of hardening schools won’t go away. Absent effective gun reform, surveillance of American children is becoming a fact of life, and their parents have little choice but to accept the consequences.

Parmy Olson is a Bloomberg Opinion columnist covering technology. A former reporter for the Wall Street Journal and Forbes, she is author of “We Are Anonymous.”