Over the past decades, the closure of urban public schools has disrupted the educational experiences of hundreds of thousands of public schoolchildren. Since 2000, urban school districts in cities such as Chicago, Cincinnati, Detroit, Indianapolis, Kansas City, Minneapolis, New York, Philadelphia, Pittsburgh, St. Louis, and Washington, D.C. have shuttered more than 20% of their public schools (Brummet, 2012; Dowdall, 2011). In the 2010-11 school year alone, urban school closures displaced over 100,000 students (Author calculations, NCES CCD). Indeed, even Texas, which has experienced sustained population growth over the past decades, has closed a number of schools, particularly in Dallas and Houston. While closures have often been motivated by declining enrollments in light of constricting budgets, districts are also increasingly utilizing closures as a reform strategy to combat chronic low academic performance. Despite the steadily increasing number of school closures and the controversial nature of closure reform, scant empirical attention has been devoted to examining the effects of closures on student outcomes. In Part I of this investigation of school closures in Houston Independent School District (HISD), the authors examine the impact of closures on the academic achievement of displaced students. Being the largest school district in Texas, HISD has also experienced the largest number of closures, closing 55 schools between 2003 and 2010. In this study, the authors compare the achievement trajectories of 4,168 students that were displaced by a closure to a comparable set of students that did not experience a closure over the same time period.