In low- and middle-income countries, private schools account for 20 percent of all primary enrollment and are rapidly gaining ground. In Pakistan, the number of private schools rose to more than 70,000 by 2015, up from 3,000 in 1982; by 2015, these schools educated 34 percent of Pakistani children enrolled in primary schools. This growth in private schooling comes at a unique moment in global education: low-income countries have managed to substantially increase enrollments at all levels of schooling, but they have yet to improve what children learn. Some people favor heavily regulating or even shutting down private schools, based on the belief that they provide substandard education to children of parents who are unable to assess the quality of schools; others believe that private schools should be encouraged and indeed subsidized through the public purse because they provide a valuable option in places with failing public schools. Missing from this debate is a detailed empirical picture of what the growth of private schools means for education markets more broadly. How does the rise in private schooling affect demand for schools in both the private and public sectors, and how do schools respond to any changing demand? Does more competition increase quality? Should governments maintain their focus on improving the quality of public schools, alleviate constraints on private alternatives--or perhaps do both?