Chile is a medium-sized developing country, with approximately 3,500,000 school-aged children. Computational thinking (CT) has been recognized as a tool for developing XXI century skills, but Chile has a large population of in-service teachers that do not know what CT is, limiting its application in classrooms. In response, the government has enacted a training program for in-service primary school teachers, focusing on changing their perceptions about CT, and showing them how it can be used in classroom. This training program was designed for grades 1-6 and piloted in the capital region during 2018. The program initially focused on coding activities, but was then redesigned to show how CT can be used to help meet the learning objectives of different subjects in the curriculum. The program was then scaled up nationwide. In this experience report, we discuss the outcomes of this program. The training program scaled as intended and we identified positive changes in teacher perceptions about CT, especially among female participants. We conclude with the lessons we learned from this experience.