Who's doing it: Long a fixture at many urban schools, they now are used in nearly 13% of all high schools, according to the National Center for Education Statistics.
Believers say: Preventing a single shooting makes them worthwhile. According to the U.S. Centers for Disease Control and Prevention, 18% of high school kids say they've carried a weapon in the last month. And students themselves are demanding more protection. In Boston, where school violence increased 14% from 2002 to 2006, a student group recently lobbied for stepped-up screenings. "When kids know there are metal detectors, I think the likelihood of them bringing weapons to schools would be diminished—significantly," says Ronan Matthew, principal of Canyon Springs High School in Las Vegas.
Critics say: "It creates an atmosphere of degradation," explains Cecelia Blewer, a New York City parent of two teens. "I hate that we make kids start the day with something that says, 'We assume the worst about you.' It makes them think, 'Well, if the school doesn't trust me, I'm not going to trust the school,' and that affects how well they learn." Besides, she says, "anything can be used as a weapon—fists, books, a chair. The focus also needs to be on the climate at school."
Reality check: There's little evidence that detectors can stop determined shooters. And kids know that. A recent National Economic & Social Rights Initiative (NESRI) survey of teens found that fewer than half of those attending schools with metal detectors felt safer because of them. And there may be a better approach: "The number one way we find out about weapons in schools is when kids trust an adult enough to tell him or her that another student has one," says Ken Trump, president of National School Safety and Security Services in Cleveland. "Teachers, administrators, safety officials and support staff have to make it a point to interact with students and build positive relationships."