• Purpose: This paper elaborates on the commonality between the Theory of Didactical Situations (TDS) and lesson study to propose a model of lesson study using both the predominant graphical representation of lesson study by Lewis and the model of the didactical situation at the heart of TDS by Brousseau.
• Design/methodology/approach: Starting by describing and adapting the predominant graphical representation of lesson study by Lewis and the model of the didactical situation at the heart of TDS by Brousseau, the paper integrates the two representations to highlight the commonalities between the students’ learning situation and the teachers’. Based on this integrated graphical representation, the key phases of lesson study are then conceptualised by the mean of the dialectic between didactical and adidactical situation.
• Findings: The reflection about the use of the TDS graphical representation embedded in the lesson study diagram helps the reflection on the use of TDS itself to analyse lesson study. This theoretical analysis describes the process of teacher learning in lesson study and the link between their learning and the student’s. It also shows that lesson study is a good candidate for the fundamental situation of the knowledge for teaching.
• Originality/value: The graphical conceptualisation of lesson study as a learning situation for teachers offers new insight about how teachers learn in lesson study.