SUMMARY
Background: Being able to assess what is happening in a teaching-learning process is one of the teacher's competences. Teachers often must analyse and select the educational resources they consider relevant for their students. Since textbooks are an important tool for instructional design, the teacher must be able to analyse their suitability, identify limitations and make adaptations to overcome them. Objectives: This paper describes the design, implementation, and results of a training action with prospective primary education teachers, aimed at the development of competence for the analysis, identification of conflicts and proposals for the management of textbook lessons, particularly the content of proportionality. Design: The research is interpretative and exploratory, using content analysis to examine the participants' response protocols. Setting and Participants: The experience was carried out in the framework of the Primary Education grade; the sample consisted of 48 students. Data collection and analysis: Data were collected by observer/researcher annotations and participants’ responses to the proposed assessment task. Results: The results show that trainee teachers make progress in identifying conflicts and make suggestions for improvement to increase didactic suitability in the different facets, but that they are not specific enough when describing effective conflict resolution proposals, especially in the epistemic and cognitive facets. Conclusions: For future teachers to become more proficient in the mode of use, it is necessary to reinforce their didactical-mathematical knowledge of proportionality.