Abstract

• The purpose of the study was to investigate the effects of using van Hiele model on teaching geometry at the basic education high school level. A quantitative research method was used to compare the geometry achievement between the experimental group and the control group. The design applied in this study was one of the quasi-experimental designs, nonequivalent control group design. The students from the experimental group were taught by van Hiele model while those from the control group were taught by conventional method. To explore the effects of this model, the subjects were (218) Grade Ten students from two Basic Education High Schools in Amarapura Township. The sample schools were randomly selected and the groups were intact groups from two classes of each school. Both groups were administered a pretest to determine initial group equivalence before the treatment begins. After the treatment, the sample students were administered the posttest. To show statistically, the data obtained from the posttest was analyzed by using independent samples t test. The results revealed that there were significant differences in geometry achievement between the students who were taught by van Hiele model and those who were taught by conventional method in answering remembering, understanding, applying and analyzing level questions. By using the d family of effect size measures, the effect size, 1.09 for both schools were much larger than typical. It was apparent that the students of the experimental group got better levels of geometry achievement in applying and analyzing levels than remembering and understanding levels. These findings proved that van Hiele model had a positive effect on geometry achievement, and it is more effective in teaching geometry at the basic education high school level.