Teachers’ engagement with language practices through a geometry lesson study

Our study focuses on teachers’ engagement with language practices through their participation in an adapted lesson study (LS) focusing on introduction to the concept of similarity and the meaning of ‘similar’ in a lesson on similar triangles. We use data from textbook analysis, lesson planning, lessons and lesson reflection sessions to explore teachers’ engagement with language practices and how these evolved over a LS cycle. Working with the notion of dilemmas in teaching as ‘sources of praxis’ (Adler, 1998), we identified inter-connected teaching dilemmas, engagement with which led to a wider use of language registers and representations in the second lesson and with these, opening opportunities for elaborating the meaning of similar triangles. We describe the dilemmas that emerged and their related language practices, evidence teachers’ engagement with these in their talk and their teaching, and argue that LS can create conditions for teachers’ learning about language practices in teaching. • Teachers' participation in an adapted lesson study confirmed language-related dilemmas as sources of praxis. • An empirical illustration of the intertwining of representations and the language register in use in teaching 'similarity'. • Simultaneously the illustration makes visible the intertwining of the language-related dilemmas of mediation and transparency.