Because much education through ESL takes place in broader contexts of development, this article explores the links between areas often dealt with separately, namely, language, literacy, education, and development, particularly national economic development. We characterise the contrasting histories of rich and poor countries and discuss definitions of development, poverty, literacy, and L1. We review evidence showing that education and literacy are more effectively achieved in a known language, and that effective education contributes to both economic and human development. Education in poor countries, however, is ineffective, one reason being that students have an insufficient understanding of the instructional medium (typically English or French). Unfortunately, the status quo is maintained because of political priorities of unification and modernisation, and parental pressure. Development depends on an interdependent complex of economic, social, and educational factors that combine to produce vicious or virtuous circles: Effective education at the primary level, implying the use of a language understood by the students, is therefore crucial.