This paper reports on a part of a study which was conducted to determine the effect of van Hiele theory based instruction in the teaching of geometry to Grade 10 learners.

The sample consisted of 359 participants from five conveniently selected schools from Mthatha District in the Eastern Cape Province. There were 195 learners in the experimental group and 164 learners in the control group. The experimental group was given van Hiele theory based geometry instruction and the control group were exposed to the traditional method of geometry instruction. The researchers administered a multiple choice geometry test to the participants before and after five weeks of instruction (pre- and post-test design).

The results indicated a statistically significant difference between the groups. An inspection of the mean revealed that these were higher for the experimental group.

The significant improvement in the performance of the experimental group having more learners at level 2 than at level 0 and level 1 suggest that the van Hiele theory based instruction had a positive effect compared to traditional instruction. This suggests that lessons following van Hiele theory based instruction seem to raise learners' level of thinking.