This article presents results of an investigation developed as part of a Master's Thesis (Bortolai, 2010) that aimed to report on the resignification of the concept of transformation by first-year students of a governmental high school located in the city of S o Paulo (S o Paulo State, Brazil). The activities selected for analyzing the reframing of this concept were, at first, performed individually by the students. Afterwards, a discussion was held among the students, together with the school teacher, to prepare a collective synthesis, pointing to more specific features of the systems before and after the transformation process. Then, two other activities were proposed that aimed to probe the redefinition, by the students, of the concept under study. This provided the data for verifying the stages of thought processes for concept formation in adolescents, along the lines of Vygotsky’s proposals (2005). It was observed that some of the students require further discussions to change their ideas in order to achieve the stage of conceptual thought, through the mobilization of their superior mental functions.