MISTAKE-HANDLING ACTIVITIES IN THE MATHEMATICS CLASSROOM: EFFECTS OF AN IN-SERVICE TEACHER TRAINING ON STUDENTS' PERFORMANCE IN GEOMETRY

In a quasi-experimental study with 619 students from 29 classrooms (grades 718) we investigated the effects of a teacher training on teachers' mistake-handling activities and students' learning of reasoning and proof in geometry. Teachers of the experimental group classrooms received a combined training in mistake-handling and teaching reasoning and proof whereas the teachers of the control group classrooms only took part in a training on teaching reasoning and proof Their students participated in a pre- and post-test. Moreover, they were asked to evaluate how the teachers handled their mistakes. Our findings show that the teacher training was successful: the teachers of the experimental group classrooms changed their mistake-handling behavior and, compared to the control group classrooms the students in the experimental group performed significantly better in the post-test.