Development of geometric thinking of elementary school mathematics teachers: A lesson study

The general purpose of this study is to investigate the development of geometric thinking of elementary school mathematics teachers. For this purpose model of research is defined as lesson study. The implementation process of the study, in the academic year of 2013-2014 and at elementary school in the city center of Aydın was carried out with five mathematics teachers from different schools. Firstly, a five-week seminar process was carried out with teachers within this process. In this seminar, lesson study was explained with Geometric Habits of Mind theoretical framework and practices about development of Geometric Habits of Mind were implemented. Then lesson study takes about 3-monts was performed. Two months after period of lesson study, individual lessons of teachers performed in their schools has been observed for 2 weeks and investigated whether they gain geometric habits or not. Data was collected by using multiple data collection tools, such as "video recordings", "teacher observation notes", "researcher field notes" and "interview records". Data analysis was carried out in two stages as in the data collection process and after data collection process. In the analysis of the video data, video analysis model developed by Powell, Francisco and Maher (2003) was used. As a result of this study, geometric thinking of teachers has improved through lesson study. In the process from first lesson study to seventh lesson study, that improvement of mathematical language used by teachers, representations, student inquires in class, activities and problems based on geometric habits of mind for the relevant concepts produced by teachers, produced these problems and instructional processes by considering these components assessed by teacher and their own geometry lessons in this framework planned and implemented by teachers was determined. After lesson studies, also that teachers considered geometric habits in their own school settings and they reflected on instructional process through prepared activities and problems was determined. Key words: Geometric habits of mind, geometric thinking, lesson study, teacher professional development