AbstractIn this study, we intend to characterize the productive engagement of students during the use of computer simulations in the classroom, and identify and describe the factors that influence it. Our principal aim is to understand how the teacher's mediation in classroom with students using computer simulations influences the students’ productive engagement. There are described two teacher cases. It was collect several types of data about two lessons per teacher. The two teachers of physics and chemistry have similar professional experience, but different experience integrating educational research in their teaching practices. The results allow us to find the fundamental conditions to engage students productively when they use CS and t...