The effects of teacher professional development model aiming at geometric thinking on student Van Hiele levels of geometric thinking in secondary classes

In this thesis, the effect of a professional development program which aims developing the habits of geometric thinking in secondary school teachers and students on students' levels of van Hiele geometric thinking is studied. Through in service-trainings which include thirty two Maths teachers who work in state schools in Gaziantep, it is aimed to develop the geometric thinking of the participants and their students by this model. Within the scope of the program, initially, the activities the purpose of which is to develop geometric thinking are performed by the teachers who join the training. After negotiating on the activities, the teachers are asked to apply these activities in their classes. Ten volunteer teachers from different schools are selected among thirty two ones. The classes in which these ten teachers applied the activities are selected as experimental groups; the classes of other teachers in the same schools who don't join the training are selected as control groups. The van Hiele geometric thinking level test is applied to 20 classes in total before and after applying the activities. The data received simultaneously from the teachers in each school is analyzed by the statistics program. While analyzing the data, t test, covariance analysis, and chi-square test are used. The findings obtained reveal that before the training the geometric thinking level of most students is low and after the training it stays the same. Key Words: Teaching Geometry, Habits of Geometric Thinking, van Hiele Geometric Thinking Levels