Abstract Around the world, growing attention focuses on the scale, nature, and implications of private supplementary tutoring. This phenomenon has long been especially visible in East Asia and is now global. Some tutoring is provided by commercial enterprises, but other tutoring is provided by regular teachers seeking to supplement their incomes. University students and other informal suppliers are also evident. In contrast to government-led initiatives, most shadow education has developed despite rather than because of government policies. Indeed it could be described as privatization by default. The tutoring sector has grown in response to demand from students and their families and through the entrepreneurial initiatives of companies, teachers, and informal providers. From the perspective of mainstream schooling, private tutoring is not simply a parallel supplement; it has far-reaching implications for mainstream schooling as well as for wider social and economic development.