Allowing students to transfer to schools across district lines is gaining more attention as a strategy for reformers looking to reduce economic and racial segregation in public education and give students in failing schools a better chance to achieve, and a number of organizations have endorsed the idea. Interdistrict choice, advocates assert, would allow students in low-performing schools to move to higher-performing schools with very different economic and racial profiles. Many advocates have pushed for including interdistrict choice in the federal No Child Left Behind Act (NCLB). The law requires that students in low-performing schools be allowed to transfer voluntarily to higher-performing schools within their school system. But because there are few higher-performing-school options for such students, only a fraction of them have been able to take advantage of the intradistrict transfer opportunity. Permitting students to move further, beyond school system boundaries, is unlikely to increase most students' educational opportunities significantly. Using Geographic Information Systems (GIS) mapping technology of school performance information in California, Texas, and Florida, Education Sector has found that factors such as long distances to higher-achieving schools and limited capacity in such schools can sharply limit the ability of students to take advantage of interdistrict opportunities. Studies of existing multidistrict choice programs have found that a lack of information for parents and inadequate transportation subsidies also limit the scope of many interdistrict choice programs. To date, there is limited research evidence to support the premise that moving students to a higher-performing school alone will result in improved student achievement: many interdistrict choice programs have failed to produce the improved student performance and socioeconomic integration that interdistrict choice advocates envision, and some may have increased racial segregation. Permitting students to seek out higher-performing schools in other school systems would enhance the educational opportunities of some students. But even under the best-designed interdistrict choice programs, the majority of students will remain in the same low-performing schools. Ultimately, policymakers will have to pursue additional solutions. Information on methods is appended. (Contains 48 endnotes, 10 maps, and 6 figures.)