Maria Heavener had opened the windows of her first-grade classroom to let in the unusually warm October breeze when the sound of helicopters, sirens, and a flood of notifications compelled her to slam them shut. During a raid on a nearby grocery store, U.S. Immigration and Customs Enforcement agents had hurled tear gas canisters into a parking lot across the street from Chicago’s Funston Elementary School, spreading a thick, choking smog toward the building while class was in session.