Over the past decade, developmental theory has occupied a central role in science education instructional theory and empirical research. The purpose of the present study is to quantitatively synthesize studies relating age (or grade) and developmental level to science learning among grade 6-12 students over the 1963-1978 period. Twenty-seven studies were reviewed. Annual increments observed in measures of developmental level were consistent with current theory, and annual increments in cognitive achievement were relatively constant over the grade 4-9 interval. Measures of student ability were found to be better predictors of cognitive achievement than developmental measures; age and grade level were weakly related to developmental level and cognitive achievement, showing only significant correlations across grade levels.