Education is often depicted as one of the best ways out of poverty. At the same time, research over many decades finds that most educational outcomes are strongly correlated to poverty. It is not likely that these two themes are true at the same time. Either schools are windows of opportunity and help overcome or mitigate poverty and other barriers or they are mirrors of society's inequities. The question in this report is a straightforward one: Are urban public schools, which have the largest numbers and concentrations of poor students in the nation, windows or mirrors? The Council of the Great City Schools used the latest ten years of data in reading and mathematics at the fourth- and eighth-grade levels from the National Assessment of Educational Progress (NAEP) to answer this question. What they found suggests that poverty was not necessarily destiny in urban public education. Students in Large City public schools scored higher than predicted on NAEP and showed greater district effects over the study period than other schools in the aggregate across the country. These Large City School students were about 50 percent more likely to be poor, twice as likely to be English learners, twice as likely to be Black or Hispanic, and about 50 percent more likely to have a parent who did not finish high school as students in All Other Schools. To explore what drove district progress, the Council conducted site visits to six districts that seemed to do a better job than others in overcoming or mitigating barriers and two counterfactual districts. Case studies of these districts indicated that those who overcame barriers to some extent benefitted from many of the same strategies and characteristics, including strong and stable leadership that was uniquely focused on student instruction; high academic standards and well-defined instructional guidance and support; human capital strategies aimed at raising the capacity of leaders and teachers; the cohesion and differentiation of professional development; the ability to act at scale; strong accountability systems and cultures of collaboration; the ability to see opportunities in the challenges they faced; their district, school and special population strategies; and their community investments and engagement efforts. [This report was written with Ricki Price-Baugh, Robin Hall, and Denise Walston.]