New teachers, new backpacks, new crushes--and algorithms trawling students' social media posts. Blake Prewitt, superintendent of Lakeview school district in Battle Creek, Michigan, says he typically wakes up each morning to twenty new emails from a social media monitoring system the district activated earlier this year. It uses keywords and machine learning algorithms to flag public posts on Twitter and other networks that contain language or images that may suggest conflict or violence, and tag or mention district schools or communities. In recent months the alert emails have included an attempted abduction outside one school--Prewitt checked if the school's security cameras could aid police--and a comment about dress code from a student's relative--district staff contacted the family. Prewitt says the alerts help him keep his 4,000 students and 500 staff safe.