Cameras streaming high-definition images over superfast mobile networks could improve security in schools and on our streets, and help cities run their services more efficiently, tech experts say. Beyoncé Brooks, a 17-year-old student at Millennium High School in Goodyear, Arizona, US, says her school has practice lockdowns each term to deal with gun incidents. She says there is "probably one real lockdown" a year at her school of 2,000 students. "Basically, we turn the lights off, the door is locked, and we all sit in the corner of the room huddled. The teachers don't really say anything, so we don't know if it's something that's real," she says.