The role of peer and teacher mediation in discussions about two original scientific texts in the final year of high school in Brazil is explored in this study. A text by James C. Maxwell, deals with the characterisation of light as an electromagnetic phenomenon, and refers to the continuous manner of the distribution of energy by radiation in space. The other, by Ludwig Boltzmann, is about thermodynamics in its probabilistic conception and some of its consequences for the comprehension of the nature of heat. We analyse some of the students' interpretations using a version of discourse analysis, developed in Brazil following the French tradition of Michel Pêcheux. We highlight interactions that contribute to the reading of the texts and the mediations of both the teacher and peers that promote the establishment of relevant meanings about physics concepts. The appropriation of their statements about the content is observed in this communicative approach. We contribute to the investigation of physics teaching using strategies informed by a humane scientific and cultural educational perspective in high schools.