Beginning in 2005, the GE Foundation initiated a commitment of expertise and financial resources to a set of urban school districts to improve public education and enhance student achievement in mathematics and science. This report analyzes the impacts of the GE Foundation commitment to the partner districts by examining trends in student performance in mathematics over time in four districts. The authors hypothesized that the GE Foundation's collaborative efforts with the district educators would produce detectable and significant improvements in student outcomes. This report analyzes the longitudinal impact of "Developing Futures"™ in four urban school districts that have worked with the GE Foundation for at least four years, including Cincinnati, Ohio; Erie, Pennsylvania; Jefferson County (Louisville), Kentucky; and Stamford, Connecticut. Using individual student records over a period of up to 10 years, the authors analyzed performance trends both before and after the GE Foundation began working with the districts to assess how student achievement in mathematics changed during the introduction of "Developing Futures"™. Overall, the authors found strong evidence that the GE Foundation's efforts significantly contributed to improvements in student mathematics test performance across the partner districts. The report includes two appendices: (A) Annual Testing Schedules by District; and (B) Annual Statistical Model.