Many secondary schools in the UK lock phones away at the start of the day. Works really well. Kids are fine with it. We have a few medical exemptions. If they need to call home they go to the school office. Kids are less distracted, not taking inappropriate pics/vids, they talk to each other at break, everyone feels safer. And fortunately we don't worry at all about guns because they've been banned. No one has one, no one gets shot.