Abstract
This dissertation presents a research conducted with in-service secondary school teachers and focusing, in particular, on the processes that unfold within a classroom when teaching combinatorics. Based on a background work that was conducted as part of my Master’s thesis and in which it was observed that students, when engaged in combinatorial problem solving activities, mainly focus on a reduced set of heuristics, the research that will be presented in this dissertation aims to investigate such phenomenon by focusing on the variable ‘teachers’. Specifically, this work consists of a concatenation of several studies that have explored teachers' perspectives and practices in relation to the subject of combinatorics in secondary school, investigating teachers' postures during teaching and towards the subject itself, together with the reasons behind their didactic choices and the processes of interpretation that are carried out on students' solutions, with the aim of providing an overall picture of teachers' process of constructing students' combinatorial knowledge and the phenomena that develop in the classroom.