Print Jai’Ree Tannan stepped onto the stage erected in the shadow of the police union’s headquarters in Los Angeles’ Westlake neighborhood. The 20-year-old stood away from the microphone, listening intently as a fellow student activist gave voice to the crowd. “We got cops off campus,” the female speaker declared. “We did that!” Tannan nodded proudly. “Woooo!” cheered the crowd that had gathered on a recent afternoon for the rally organized by Black Lives Matter Los Angeles. Following a prolonged campaign led by students, including Tannan, the L.A. Board of Education in F...