This fire-the-worst policy could have benefits beyond those calculated by Chetty and his co-authors. Economists Thomas Dee of Stanford and James Wyckoff of the University of Virginia recently analyzed Washington, D.C.’s IMPACT program, which financially rewards the best teachers and threatens the worst with dismissal. Dee and Wyckoff compared teachers who were near the thresholds for bonuses or dismissal threats with teachers who actually crossed the thresholds. They found that the highest-graded teachers performed even better as a result of IMPACT’s bonuses. The lowest-graded...