For the first time since he started teaching Welfare Economics and Social Choice Theory nearly two decades ago, Brown University economics professor Roberto Serrano gave his students a take-home midterm this spring. Quite a few students had expressed anxiety about being in a classroom after a gunman killed two students and injured nine in a December mass shooting at Brown, and so “it was appropriate,” he said, to allow students to take their exams at home. But by the end of the semester, Serrano...