This paper seeks to measure the effect of women teachers' professional training on the quality of classrooms and early literacy among pre-school pupils in Chile. The randomly chosen groups included 24 public schools and 240 pupils. The Early Language and Literacy Classroom Observation (ELLCO) toolkit was applied to measure the before/after quality of literacy in pre-school classrooms. The before/after early literacy of individual schoolchildren was assessed using the Early Literacy Test (Prueba de Alfabetización Inicial, PAI). This intervention consisted of a program for teaching staff, including a seminar on updating teaching methods and direct classroom supervision, during one semester. A difference-in-differences, d-Cohen and multilevel data model was used to identify the effects. The results show significant progress in four aspects of classroom quality for teaching literacy: "general" quality, "language", "understanding of printed matter", and "literacy". There was no impact on individual literacy.