Houston is thinking big. In the Bayou City, philanthropists are leading a Texas-sized effort to dramatically grow KIPP and YES Prep, two of the nation's most successful charter school networks. Their goal: within ten years, to serve 30,000 students annually. If they succeed, 15 percent of all Houston public school students will be in schools with an amazing record of sending low-income students to four-year colleges. How are funders ensuring that growth doesn't diminish quality? And what are the implications for large urban school districts nationwide?