The belief that with hard work and determination, all children have the opportunity to succeed in life is a cherished part of the American Dream. Yet, increased inequality in America has made that dream more difficult for many to obtain. In Too Many Children Left Behind, an international team of social scientists assesses how social mobility varies in the United States compared with Australia, Canada, and the United Kingdom. Bruce Bradbury, Miles Corak, Jane Waldfogel, and Elizabeth Washbrook show that the academic achievement gap between disadvantaged American children and their more advantaged peers is far greater than in other wealthy countries, with serious consequences for their future life outcomes. With education the key to expanding opportunities for those born into low socioeconomic status families, Too Many Children Left Behind helps us better understand educational disparities and how to reduce them.