This book examines a policy that is one of the most powerful levers to improve teaching quality and advance teaching as a profession. Jennifer Goldstein presents the story of Rosemont, an urban district in California that created ""professional accountability"" with peer assistance and review (PAR), an alternative approach to teacher evaluation in which expert teachers evaluate their teacher peers. It challenges a number of long-held beliefs and practices in education-- adversarial labor relations, ""being nice,"" hierarchy, isolation, and negligence--to achieve very different teacher evaluation outcomes. This timely and accessible volume: Chronicles a rare case of a teacher union and school district partnering to improve teacher quality and teacher evaluation. Presents the most detailed study of PAR implementation, including its processes, challenges, and outcomes. Summarizes the state of PAR implementation across the country in an afterword by Susan Moore Johnson.