This literature review summarizes and integrates the existing knowledge on early childhood education and preschool programs in order to assess under what conditions the preschool has a positive impact on cognitive and social development of preschool children and their subsequent school achievement. Four basic conditions emerge from the literature for a quality preschool education in disadvantaged contexts: 1. relevant teaching models, 2. an education rooted in local culture, 3. involvement of families and communities; 4. programs of health and nutrition related to preschool.