This study describes the implementation of a program to enhance phonological awareness in Kindergarten Chilean students from a low-income background. The intervention included a special professional development course designed for teachers, to help them reflect and modify their practices, where classroom observations and feedback on instruction became a fundamental basis of the intervention. Children were assessed before and after the interventions, and results were compared with those of a control group. Results reflected how teachers’ practices are a fundamental key to understanding children outcomes, and that immediate feedback is fundamental for instructional change that favors learning.