In February, two school districts in South Carolina became the first in the country to install body scanners at the main entrances of their schools. Florence District 1 and Spartanburg District 6, Motherboard reported, replaced their clunky metal detectors with Evolv Technology’s airport-style scanners, after a monthslong initial implementation phase at Spartanburg schools.

Evolv claims that these machine learning scanners are the world’s “fastest, most accurate and least intrusive weapons detection systems,” with the capacity to screen thousands of people per hour. They’re also free-flow: Students can pass through them without even slipping off their backpacks, the way they would have to with a metal detector.

In the first 46 weeks of 2019, there were 45 school shootings in the U.S. As policymakers, educators, parents, and students continue to seek a greater sense of control and agency amid this gun violence in schools, a variety of new tech products have entered the market, including facial recognition systems, spyware that monitors students’ internet behavior, and A.I.-based surveillance cameras that track suspicious movement. Still, people haven’t yet given up on old-fashioned metal detectors, which first became popular in U.S. airports in the 1970s and in some school districts in the 1990s and 2000s, despite questionable results. In February, for instance, Rep. Wendell Gilliard, a Democrat from Charleston County, filed a bill to the South Carolina House of Representatives that would require metal detectors in every public school in the state. A similar bill was introduced to the Texas House in 2019.

While neither Florence nor Spartanburg has previously dealt with a shooting, the districts have experienced threats and a lockdown in the past couple of years. Mark Smith, the director of student services and safety at Spartanburg 6, said in an Evolv press release that he came across the company when he was searching for “a solution that delivered optimal security while providing a welcoming, non-prison-like environment for everyone on campus.”

But there are concerns about efficacy—and cost. No public data is available on the scanners’ accuracy, and Florence 1’s superintendent has said that they cost $364,000 for a four-year lease. As Amelia Vance, director of youth and education privacy for the Future of Privacy Forum, told Motherboard, after the Parkland shooting in 2018, schools have been flooded with expensive technology proposals “that have no evidence base behind them.” It’s possible that schools are funding a pipe dream at the expense of potential programs and faculty. “Any time you’re spending money on something you’re taking money away from more school counselors,” Vance said.

And then there is the issue of privacy. Evolv says its scanners can pinpoint exactly where a weapon is on the body. Similar to airport scanners, this raises questions about whether—and to what degree—it’s acceptable to reveal the contours of a child’s body to security guards. Additionally, machines like this further underscore the extent to which children are being monitored, especially by technology neither they nor we yet understand. There’s something unsettling about the brunt of the state and federal governments’ failures to enact better gun control policy falling on schoolchildren.

It’s not uncommon to hear nostalgia for ye olden days, when one could waltz up to an airplane, briefcase and full-size shampoo bottles in tow, and board. No lines, no scanners. In this case, though, it’s not consultants or businesspeople who fly regularly for work that are most affected by new security measures. It’s children who can no longer get to class without being reminded, once again, of their own mortality.

Future Tense is a partnership of Slate, New America, and Arizona State University that examines emerging technologies, public policy, and society.