Description: Our paper focuses on the description and analysis of objects being taught in French first language classrooms. We refer to a large research (FNRS 1214-068110) we have conducted in three French speaking Swiss cantons. Based on a didactic transposition theoretical framework we are interested in the transformations an object to be taught may undergo when it is actually taught in the classroom and we have investigated teaching practices on argumentative texts and relative clauses, two different objects appearing in the secondary school curriculum. Methodology: After a short presentation of some aspects regarding data collection (video-recording of teaching sequences constituted of several lessons and transcription) we will present our methodological tools to describing and analysing French first language objects being taught in classrooms. A two-step method has been built. First, a synopsis of each teaching sequence has been made. Second, a multifocal description of the object being taught has been provided for: a) outlining each sequence through its macrostructure and the enchainment of its school activities; b) highlighting some fundamental teaching gestures like evaluation and institutionalization, observed throughout the sequences; c) observing the crossover flow between sub-disciplines involved in mother tongue education (grammar - writing; reading - argumentation). Conclusions: Results seem to indicate that our method provides us with answers concerning how an object to be taught becomes an object actually taught in French first language classrooms and draws attention to the contributions a didactic approach may offer to the understanding of teaching practices in first language classrooms.