The effectiveness of a principle-based professional development programme in promoting teachers' high-level talk in primary mathematics classrooms.

Introduction: We investigate whether a principle-based professional development programme can effectively promote teachers' talk in primary mathematics classrooms. The programme aimed to implement accountable talk (AT), integrating three design principles: (a) incorporating authentic classroom episodes, alongside individual and collective reflection; (b) long-term duration; and (c) video-based discussions.

Methods: We analysed the classroom talk of eight teachers of different ages, seniority and academic background at three timepoints: before, during and at the end of the programme, focusing on teachers' AT quality at both macro- and micro-levels. The macroanalysis concerned ratings of teachers' talk as a whole, while the microanalysis inspected teachers' specific AT moves. This enabled us to assess how teachers operated AT moves to raise the level of discussions and advance student learning.

Results: Both averaged macro-level ratings and rates of micro-level talk moves attest to an overall improvement in teachers' AT quality over time. However, improvement appears durable mainly for older, more senior teachers with specialized mathematics education. The macroanalysis reveals significant improvement in teachers' accountability to the learner community, alongside a strong positive correlation between the level of cognitive demand maintained by the teacher and the overall quality of teachers' AT. The microanalysis reveals significant improvement in teachers' accountability both to the learner community and to mathematical knowledge and reasoning.

Conclusion: Beyond the overall improvement of the quality of teacher talk over time, micro- and macro-analyses reveal differences attributable either to the sensitivity of the methodological tools or to the nature of the change in teachers' practices.