PurposeThis study examined participating teachers' expressions about teaching and learning when implementing lesson study (LS) about communication as a special didactic tool in mathematics; it also investigated their experience with LS. The initializing phase was characterized by letting the teachers become familiar with LS as a model for their professional development (PD). It also provided an opportunity for the participants to acquire common understanding of their starting point.Design/methodology/approachAn adapted version of LS was used as a model for teachers' PD. The methods for data collection were a semi-structured interview and discussions with the teachers. From a teaching team in school year 1, two class teachers participated. The data obtained were qualitative and subjected to a thematic analysis. The teachers participated together in the different discussions during the study. All the discussions were audio-recorded.FindingsDuring the discussions, the teachers raised some critical points: how to gain students' attention during lesson reviews; how to make follow-ups of the students' understanding of lesson content; how to plan and factors that could have been changed in education that could assist in all students' progress.Originality/valueBoth the initializing phase and the concept of special didactics have not received full attention in research. This study highlights the importance of capturing the teachers' attained competence toward understanding what is needed for future competence concerning communication as a special didactic tool in mathematics.