Few topics in education inspire as much debate as charter schools, which first appeared on the educational landscape in 1992 and now include some 3,500 schools operating in 40 states. Fueling this debate are recent studies of charter school student achievement (Buddin and Zimmer, 2005; AFT, 2004; Booker et al., 2004; Sass, 2005; Hoxby, 2004; Bifulco and Ladd, 2005a; Hanushek et al., 2002). While these studies have been informative, they generally have not shed light on a broader set of questions, including the effect charter schools have on the distribution of students by race/ethnicity and ability. Charter school critics argue that charter success might be illusory if charter schools are simply recruiting the best students from traditional public schools and that charter schools may further stratify an already racially stratified system. One way to address these concerns is to analyze the effect of the redistribution of students to charter schools on the dynamics of peers within traditional public schools. In this study, the authors examine charter and traditional public schools in California and Texas. In both states, they have student-level data over time with unique identifiers, which allows them to track students as they move between traditional public schools and charter schools. They find that black students in both states are more likely to move to charter schools and tend to move to charter schools with a higher percentage of black students, and those schools are more racially concentrated than the public schools they leave. They also find that students who move to charter schools are on average lower performing than other students at the public schools they leave and that this performance gap is largest for black students.