The main objective of the study was to investigate the process of building scientific concepts, specifically in a classroom environment, using the methodology of the General Theory of Activity from the Russian psychopedagogist Alexei Nikolaivich Leontiev (1903-1979), supported by the Historical-Cultural Theory from Byelorussian Lev Semienovitch Vigotski (1896-1934), with interlocution with the Assimilation Theory from Piotr Yakovlevich Galperin (1902-1988). The assumption that conducted the research was that structured teaching, according to the principles of Historical-Cultural Theory, favors the process of building scientific concepts, by promoting the development of higher psychological functions, the structuring of consciousness and the formation of personality. It started with the following question: how does the process of constructing scientific concepts, specifically, in the classroom environment, take place? The empirical part of the study was developed in the city of Corumbá (Mato Grosso do Sul, Brazil), in a state school, in three first-grade secondary school classes and their teachers. Some teaching sequences where accompanied and analyzed during the Biology classes. The method used was dialectical; the data collection instruments were: semi-structured interviews, questionnaires and field diaries. The study provided evidence that the issues related to motivation, contextualization of concepts, evaluation function and the role of secondary education in basic education are fundamental aspects to be considered in the teaching-learning formation process of scientific concepts. It also demonstrated that the General Theory of Activity constitutes a valuable resource for the analysis of the educational process, especially the one related to the formation of scientific concepts.