With income inequality at record levels (Mishel et al. 2012), the interactions between poverty and race remain strong and troubling and continue to impede educational progress for many students. One result of such interactions is ongoing segregation--at both the neighborhood and school levels. Yet most education "reforms" focus on a narrow set of policy fixes that minimize the roles of poverty and of race and overlook the impact of segregation. As scholars document the connections between neighborhood- and school-level segregation, it is important that we better understand how both affect schools and students in order to more productively guide both future research and policymaking. This paper uses data from a recent representative cohort of U.S. students entering kindergarten--the National Center for Education Statistics' Early Childhood Longitudinal Study, Kindergarten Class of 2010-11 (ECLS-K:2011)--to begin to do that. We first describe how segregated schools are by both race and income, by comparing the racial and socioeconomic status (SES) composition of those kindergarten classes with what they would look like if they represented the characteristics of the U.S. student body overall. We then explore the differences in students' other characteristics based on the racial makeup of their own classes. Finally, we analyze how their academic performance changes over that first year (as measured by their place on the score distribution in math, reading, and approaches to learning at entry in the fall and again in the spring) by level of segregation in the school. (author abstract)