This working paper series examines the politics of portfolio school district reform, with a primary focus on the issues surrounding high school closures. The authors take an in-depth look at how school closure policies have played out in four urban districts—New York City, Chicago, Denver, and Oakland—and offer a political assessment of what worked or failed and why. The political analyses, case studies, cross-district comparisons, and analysis frameworks may help education leaders anticipate and better address the challenges of closing schools within their own communities.