There is a lively debate about the extent to which private providers of educational services can contribute to the achievement of Education for All and the Millennium Development Goals. There is evidence that in some poor countries private provision has been growing especially at the secondary level. The reasons for this are not simple but include excess demand (more applicants than places), differentiated demand (preference for alternatives to existing public schools), and the opportunities created for entrepreneurs by newly liberalised regulatory frameworks for educational services. This paper identifies a range of constraints and contextual realities that will shape future development. The first section draws attention to the diversity of non-government private provision and some fundamental issues that shape its likely contribution to enhanced access to schooling. Second, estimates are presented of the numbers of children currently out of school and their location in Sub-Saharan Africa. Third, data is discussed which illustrates the extent to which exclusion is related to wealth, location and gender, focusing on economic constraints. Fourth, costs related to teachers are modelled to indicate likely minimum operating costs for unsubsidised schooling. Fifth, an analysis is offered of the underlying demographic realities of expanded enrolment to reinforce the need to understand the magnitude of the task of achieving the MDGs and the need to identify mechanisms that expand services to large numbers of school-age children drawn from the poorest households. Finally some concluding remarks draw together the arguments.