In recent decades, K-12 school discipline policies and practices have garnered increasing attention among researchers, policymakers, and educators. Disproportionalities in school discipline raise serious questions about educational equity. This study provides a comprehensive review of the extant literature on the contributors to racial, gender, and income disparities in disciplinary outcomes, and the effectiveness of emerging alternatives to exclusionary disciplinary approaches. Our findings indicate that the causes of the disparities are numerous and multifaceted. Although low-income and minority students experience suspensions and expulsions at higher rates than their peers, these differences cannot be solely attributed to socioeconomic status or increased misbehavior. Instead, school and classroom occurrences that result from the policies, practices, and perspectives of teachers and principals appear to play an important role in explaining the disparities. There are conceptual and open empirical questions on whether and how some of the various alternatives are working to counter the discipline disparities.