Abstract: The study aimed at investigating the impact of a Cabri learning environment on the level of reasoning in geometry and whether this impact affects differentially grade eight students of different levels of math achievement. The teaching experiment involved an experimental group (Cabri environment) and a control group (Cabri–free) environment. The Structure of Learned Outcomes (SOLO) taxonomy was used to assess the reasoning level in the student–produced proofs of the posttest. Two scores were generated from the posttest scores: A SOLO score and a SOLO level score. The results indicated that: (a) there was a significant difference between the control and experimental group on the SOLO score in favor of the experimental group and this difference was more pronounced for the low achievers than high and average achievers; (b) the percentage of students at the pre–structural SOLO level was less for the experimental group than that of the control group whereas the percentage students at the multi–structural SOLO level was higher for the experimental group than that in the control group. The findings were interpreted theoretically and empirically.

Key words: Cabri; Computer learning environment; Teaching experiment; Reasoning