School spending on physical security hardening is now a $4-billion-a-year market in the US, but Jennifer DePaoli of the Learning Policy Institute argues the evidence base for safer outcomes is thin. Singlewire's survey of 500 staff finds 46% of schools report insufficient security personnel — up from 30% last year. DePaoli cites cases where surveillance flagged a clarinet as a weapon, and where school camera data was handed over to federal immigration enforcement.