Teachers’ Development of Didactic and Algebraic Praxeologies through Bi-Institutional Lesson Study

Transition problems in algebra between Danish lower and upper secondary school point to a need for teachers from different institutions to develop shared didactic and mathematical knowledge. The article presents bi-institutional lesson study, based on the anthropological theory of the didactic, and examines its potential for supporting teachers’ development of shared knowledge of these transition problems. Despite structural asymmetries, the collaboration provided learning opportunities for both groups, helping teachers identify common challenges, such as students’ use of guess-and-try methods when solving first-degree equations and difficulties with algebraic rules. Designing tasks requiring algebraic manipulation proved more difficult than expected. Teachers emphasized the importance of designing algebra tasks accessible to students with varying prior knowledge. The findings indicate a need for external inputs and further cycles of bi-institutional lesson study to achieve more substantial development of shared praxeologies, highlighting the limitations of what bi-institutional lesson study can achieve on its own.