Abstract
Pupils in eight schools were given special lessons within their science curriculum based on notions of cognitive conflict, metacognition, and bridging set in the context of the schemata of formal operations. These special lessons replaced regular science lessons once every 2 weeks for 2 years. Results of tests given immediately after the intervention and 1 and 2 years later, standardized with respect to pretest scores of experimental and control pupils, indicate that the intervention led to immediate gains in Piagetian measures of cognitive development and to gains in experimental groups' achievement in science, mathematics, and English language measured 2 and 3 years after the end of the intervention program. Groups most affected included the boys who started the program in Year 8 (Grade 7) and the girls who started in Year 7 (Grade 6). There were stronger effects of girls' gains in English achievement and on boys' gains in science and mathematics achievement. We explore possible explanations for the results in terms of underlying domain-specific or domain-general cognitive structures.