We study a program designed to encourage learning from coworkers among school teachers. In an experiment, we document gains in job performance when high- and low-skilled teachers are paired and asked to work together on improving their skills. Pairs are matched on specific skills measured in prior evaluations. Each pair includes a target teacher who scores low in one or more of 19 skills and a partner who scores high in (many of) the target’s deficient skills. Student achievement improved 0.12 standard deviations in low-skilled teachers’ classrooms. Improvements are likely the result of target teachers learning skills from their partner. (JEL I21, J24, J45, M53)