“The school safety and security industry has grown rapidly over the past decade,” says Sonali Rajan, senior director with the research arm of Everytown for Gun Safety, which advocates for gun control. “The challenge right now is that these school safety products, the vast majority, have absolutely no evidence guiding their effectiveness.”

Inside the school safety conference, vendors in an expo hall showcase panic buttons, bullet-resistant whiteboards, facial recognition technology, training simulators, body armor, guns and tasers.