The Distribution of Piagetian Stages of Thinking in British Middle and Secondary School Children

S ummary . The proportion of children showing early and late concrete operational thinking, and early and late formal operational thinking was measured in a sample of 10,000 children between the ages of 9 and 14. The test instruments were a form of group test called Class Tasks, derived from the individual interview situations described by Piaget. These tests indicated that most children in early adolescence showed rapid development in concrete thinking, but that only one‐fifth of the children showed the further development of formal operational thought. The representativeness of these findings was ensured by relating the distribution of Piagetian stages at each age‐level to the norms of a standardised non‐verbal reasoning test.