This study investigates whether the generation of exploratory talk in grade seven, second-language science classrooms in the Eastern Cape Province, South Africa, has a positive effect on learners in terms of their problem-solving and reasoning skills and whether socio-cultural "milieus" (urban, peri-urban and rural settings of schools) have an effect on any cognitive gains that may be made by learners. The findings were that there is a clear and statistically significant improvement in the mean test scores on problem-solving and reasoning of pupils who participated in the classroom discussion initiative (exploratory talk) over those of the comparison groups. This result was consistent in both the first- and second-studies that were undertaken. There was also a significant difference between the gains in problem-solving and reasoning test scores of the three socio-geographical settings in which the participating schools are found.