Abstract
Items from a widely used standardized reading achievement test were rated by trained judges according to the degree to which they required an understanding of hierarchical classification. 2 subtests were constructed from subsets of items that were identified by their extreme ratings: Subtest A was judged to require classification operations from respondents; Subtest B, not to require them. 22 third graders were assessed on 5 types of Piagetian classification tasks. After Guttman scaling, each was assigned a single score for classification ability. Stepwise multiple regression analysis revealed that classification ability was significantly predictive of Subtest A performance, even when performance on Subtest B was controlled statistically. The results were interpreted to mean that reading test performance is partially influenced by one's mastery of hierarchical classification because some test items require this ability. Such items probably discriminate among children on the basis of developmental maturity rather than on instruction-related knowledge.