Revisiting direct proportion through lesson study

Purpose This study aims to explore how an experienced mathematics teacher restructured her pedagogical understanding of direct proportion through a dialogically mediated lesson study (LS) process. Design/methodology/approach This study reports a qualitative case study conducted within an LS cycle. The participant was a secondary mathematics teacher with 21 years of experience. The process was facilitated by a mathematics teacher educator positioned as a Knowledgeable Other (KO) adopting a non-hierarchical stance. Data were collected through pre- and post-lesson reflective dialogues and analysed using the DLP–ILP framework. Findings The findings revealed a shift from routine-based descriptions toward interpretative and conceptually grounded pedagogical reasoning. The teacher developed a critical awareness of representation choices (e.g. decreasing patterns), conceptual boundaries and the nature of the constant of proportionality. These reflections informed the redesign of the subsequent lesson. Research limitations/implications As the study relies on teacher discourse rather than direct student data, inferences about student learning remain indirect. Future research may integrate multiple data structures to link teacher learning with student outcomes. Practical implications The findings highlight the role of non-directive reflective dialogue and the mitigation of power distance in supporting teacher learning. These findings suggest that egalitarian facilitation can support meaningful pedagogical reframing. Social implications Social implications – By foregrounding teacher voice and reflective dialogue, this study highlights the importance of creating professional learning environments grounded in trust, equality and collaborative inquiry. The findings suggest that when teachers are supported through non-hierarchical and dialogic structures such as Lesson Study, they become more responsive to student thinking and more attentive to conceptual depth. Such shifts may contribute to classroom cultures where questioning, multiple strategies and conceptual understanding are valued. In this sense, the study underscores the broader social value of dialogic professional communities in fostering more reflective, student-centred mathematics classrooms. Originality/value This study foregrounds teacher voice and conceptual reframing, contributing to the Lesson Study literature by showing how structured dialogue supported the shift from descriptive to interpretative pedagogical reasoning.