The field of early childhood education is experiencing unprecedented public investment accompanied by increasing expectations for enhanced child outcomes. To achieve such outcomes, policymakers must consider the socioeconomic and racial/ethnic composition of children's classrooms as an important component of preschool quality. This report presents the results of a review and analysis of demographic data, current research, and position statements of national early childhood organizations, emphasizing the following findings. The demographic data reveal troubling racial/ethnic and economic disparities in preschool enrollment and in the quality of preschool that children experience, which beckon policy changes to provide all families with access to affordable, high-quality preschool options. Among families who do enroll, most children attend classrooms that are homogenous in family income, and often in race/ethnicity as well. (author abstract)