The paper presents findings of primary school children's performance on classification and generalisation tasks to demonstrate the fundamental connection between their verbal thinking processes and problem-solving, on the one hand, and the practical activities of their society and culture, on the other. The results reveal that, although children generally classify (or group) objects in ways that suggest abstract categorical relations, they in fact employ heterogeneous thought processes rather than simply employing either concrete-functional or abstract-theoretical modes of thinking. In addition to the concrete and abstract modes, a third cognitive mode termed abstract-functional mode is posited as revealing the fundamental connection between verbal thinking processes and the modalities of the specific sociocultural context of these children's learning and development. The findings have crucial implications for children's schooling and curriculum development, as they call for classroom pedagogy that accounts for, and interrogates the heterogeneous nature of children's thinking and conceptual development. (Contains 3 tables and 1 figure.)