Examination of the validity of the WISC-III with urban exceptional students

To investigate the criterion validity of the WISC-III, WISC-R and WISC-III IQs of 96 urban special education students who underwent a 3-yr. reevaluation were compared. The study examined (a) differences between WISC-R and WISC-III IQs and scale scores, (b) relationships among respective WISC-R and WISC-III IQs and scale sores, and (c) WISC-III IQ differences across three exceptionalities: Learning Disabled, Mentally Retarded, and Behavioral Disorders. A related question was to assess whether WISC-III Full Scale IQs differed by race. As expected, all WISC-III IQs and subtest scores were lower than the corresponding WISC-R IQs. Correlations computed among the three scales, respectively, indicated substantial conceptual overlap (Full Scale IQ = .88, Verbal IQ = .82, Performance IQ = .81). Analysis indicated a significant difference in WISC-III Full Scale IQs with respect to race. Comparisons by exceptionality and race indicated that African-American students in the Learning Disabled and Behaviorally Disordered groups obtained significantly higher WISC-III Full Scale IQs than did Euro-American students. No significant difference was obtained on scores for Mentally Retarded groups.