Some of the most dramatic gains in urban education have come from school districts using what many call a "portfolio strategy." Others call it "reinvention," a "21st century approach," or "relinquishment." By whatever name, it generally means that districts negotiate performance agreements with some mix of traditional, charter, and hybrid public schools, allow them great autonomy, let them handcraft their schools to fit the needs of their students, give parents their choice of schools, replicate successful schools, and replace failing schools. Reformers are paying close attention to Denver, Colorado. With an elected board, Denver Public Schools (DPS) has embraced charter schools and created "innovation schools," which it treats somewhat like charters. Since 2005 it has closed or replaced 48 schools and opened more than 70, the majority of them charters. In 2010 DPS signed a Collaboration Compact with charter leaders committing to equitable funding and a common enrollment system for charters and traditional schools, plus replication of the most effective schools--whether charter or traditional. This report tracks Denver's progress on the "21st century approach," and the impact it is having on Denver Public Schools.