Education policymakers have shown increased interest in incentive programs for teachers based on the outcomes of their students. This article examines a program in which bonuses were awarded to teams of middle school teachers based on their collective contribution to student test score gains. The study employs a randomized controlled trial to examine effects of the bonus program over the course of an academic year, with the experiment repeated a second year, and finds no significant effects on the achievement of students or the attitudes and practices of teachers. The lack of effects of team-level pay for performance in this study is consistent with other recent experiments studying the short-term effects of bonus awards for individual performance or whole-school performance. (Contains 10 notes and 11 tables.)