The authors wish to thank the ESRC, the participating students, teachers and head teachers, and the large number of colleagues and postgraduates who assisted with project design, sample recruitment, data collection, and data preparation (especially Ayesha Ahmed, Annabel Amodia-Bidakowska, Sarah Baugh, Elisa Calcagni, and Helen Lancaster who helped with everything).

Running head: Impact of professional development on teacher learning Highlights 1. Three patterns of teacher learning could be identified: meaning-oriented, applicationoriented and problematic learning.2. A reliable instrument to measure these teacher learning patterns was developed.3. The study contributes to our understanding of the influence of teacher professional development on teacher learning. LessonStudy has a beneficial effect on the quality of teacher learning. LessonStudy has the highest impact on improving teachers' meaning-oriented learning.

evidence of 'supportive moves' in interactions suggest that a form of dialogic space is necessary if all teachers in a Lesson Study group are to learn from shared understandings about future teaching and learning needs.

Corresponding author: mv387@cam.ac.uk; Telephone +44 1233 767569 Highlights: The development of a reliable coding scheme for teacher learning is reported. Learning in a group has an impact on teachers' individual learning processes. Dialogic moves in Lesson Study discussions are a mechanism for learning.  Descriptive and interpretative learning processes are observed in LessonStudy. AbstractThis paper contributes to our understanding of teacher learning in the context of Lesson Study (LS), a model of professional development that involves collaborative lesson planning and evaluation. Video-recorded LS discussions of mathematics teachers based in London were analysed for this purpose. Two inter-related studies are presented: the first involved the construction of a reliable coding protocol for video analysis; the second used this protocol for coding 120 fragments of discussions amongst 91 teachers. Findings are discussed with reference to tests of reliability and results of multilevel analysis, which reveal differential effects of particular forms of interactions on learning processes.

Research into classroom dialogue suggests that certain forms are especially productive for students' learning. Despite the large number of studies in this area, there is inadequate evidence about the prevalence of the identified forms, let alone their productivity. However, scarcity is widely presumed. The overall aim of the study reported in this article was to examine the extent to which the forms are embedded within current practice in English primary schools. Video-recordings of two lessons from each of 36 classrooms formed the database, with two subjects from mathematics, English and science covered in each classroom. Each lesson was coded per turn for the presence of 'dialogic moves' and rated overall for the level of student involvement in specified activities. Results revealed that the supposedly productive forms were not always as scarce as sometimes presumed, while also highlighting huge variation in their relative occurrence. They also point to the role of professional development (PD) for teachers in promoting use of some forms.