Grade retention has been the de facto policy for children with academic difficulties in many Latin American countries [Schiefelbein, E., & Wolff, L. (1992). "Repetition and inadequate achievement in Latin America's primary schools: a review of magnitudes, causes, relationships, and strategies." Washington, DC: World Bank.]. In Costa Rica, 14.9% of public school children were retained in first grade in 2002. In a study of first grade classrooms in Costa Rica, children identified as in need of repeating first grade were found to have lower levels of reading ability [Rolla San Francisco, A., Arias, M., Villers, R., & Snow, C. (in press). The importance of reading skills, prereading skills, and family in teachers' decisions to retain children: a case study in costa rica. "Aula Abierta"]. There has been a greater focus in recent years on the importance of prevention of educational difficulties, versus repetition, as the most cost-effective and efficient way of providing educational opportunities to low-income children. There is little rigorous research evaluating the impact of different interventions on the early literacy skills of low-income children in developing countries as a way to prevent posterior academic difficulties. This experimental study evaluated the differential impact of three early literacy interventions--tutoring, classroom activities, and work with families--on the emergent literacy skills of low-income Costa Rican kindergarteners. Tutoring or a combination of all three interventions were the most effective, while providing high-quality materials to teachers without training had no impact, but more intensive interventions of longer duration will probably be needed to ensure long-term impact on first grade repetition and eventual school dropout. Continuing research will assess the impact of these interventions on student outcomes and repetition rates in first grade, as well as exploring the impact of the more intensive intervention of professional development.