To test the hypothesis that if given a curriculum designed to develop cognitive functioning and taught by strategies designed to develop cognitive skills, students would then master more sophisticated symbolic thought earlier and more systematically than could be expected if this development had been left to the accidents of experience or if school experien"e had been guided by less appropriate teaching strategies, a pretest-posttest control group design was used in addition to analysis of classroom interaction. Upper elementary school students were matched on mental and chronological age and IQ. The control group had the usual social studies curriculum and their teachers did not receive training during the study. The three experimental groups were composed of (1) students with one or more years of exposure to the Contra Costa Social Studies Curriculum and teachers who received special training in teaching cognitive skills, (2) students new to this curriculum and teachers who received special training during the study, and (3) students new to this curriculum and teachers not specially trained in teaching cognitive skills. Generally, results confirmed the hypothesis, but they were not consistent. Limitations were an unbalanced sample and difficulty in clearly identifying the more complex teaching and thinking patterns. (Included are a 54-item bibliography and some tests and materials used.) (SG)