RIVERSIDE, CA – A Riverside student was arrested Tuesday after police allege the 13-year-old girl was behind an online threat directed at her middle school. The incident in Riverside is the latest in a rash of threats plaguing California schools in recent weeks, prompting police investigations, school lockdowns and arrests of suspects as young as 11. Over the last week, authorities have also investigated non-credible threats at schools in the Bay Area and in Los Angeles, Orange, and San Diego counties.