This report examines four not-for-profit school chains, run by non-governmental organisations (NGOs) in low-income contexts. These are Fe y Alegría, the Bangladesh Rural Advancement Committee (better known by its acronym BRAC), Gyan Shala and Zambia Open Community Schools. Three of these organisations offer education at no cost (Fe y Alegría, BRAC and Zambia Open Community Schools), while the other charges very low fees (Gyan Shala). All four examples are large-scale operations running multiple schools, sometimes in multiple countries. All reach large numbers of pupils. The aim of this report is to provide insight for policymakers and others preoccupied with fulfilling: (a) the continuing and still urgent need to achieve Education for All; and (b) the pressing quest for improved quality and learning opportunities for those in school. The evidence is clear: huge numbers of children and young people still do not have access to education. Increasingly, it is apparent that even when they are in school, many students are not learning and are not leaving with even the most fundamental skills of reading, writing and basic calculation. Certain groups remain particularly vulnerable -- those in rural and challenging geographical locations, girls, children with disabilities, and children from ethnic minority groups. Each of the four school groups focused on offers its own interesting story. Collectively they provide an important and optimistic perspective on the apparently intractable challenges of achieving universal access and enhancing quality in education in developing countries. This review summarises the contribution these school chains have made to education improvements and suggests some of the key reasons behind their achievements.