being determined the opinions of the course
teacher were collected and 11-A and 11-B classrooms
with equivalent achievement level were included. Van Hiele Geometry Level Understanding Test, developed by Usiskin (1982) and translated into Turkish by Duatepe (2001), was applied on the experimental and control groups. As a result of the pretest applied on the experimental and control group no significant understanding level differences was detected between the two groups. This situation indicated that the experimental group and the control group were equivalent in terms of geometric understanding level. At the end of the experimental process “Van Hiele Geometry Level Understanding Test” was applied to experimental and control groups as the
posttest.