Competences, interdisciplinarity and contextualization became part of the discourse from the majority of educators, mainly after the issue of the Curricular Directives for High School Teaching (DCNEM) and the National Curricular Parameters (PCN and PCN+) by the Brazilian Ministry of Education. Nevertheless, this does not imply that their practices are aligned with the proposals embodied in the documents. One of the reasons for it is the difficulty in understanding those notions and in their implementation in classrooms. The present work intends to clarify some of the main ideas contained in the PCN and PCN+, namely, the notion of competences, interdisciplinarity and contextualization, from the point of view of their authors, more specifically in the area of Natural Sciences, Mathematics and their Technologies. For this, semi-structured interviews were used. The thesis that there is a rupture between the DCNEM and the National Curricular Parameters, as far as educational, political and philosophical aspects are concerned, is also argued for.