Significant factor score variability and the validity of the WISC-III Full Scale IQ in predicting later academic achievement.

The purpose of this study was to investigate the validity of the WISC-III (Wechsler, 1991) Full Scale IQ (FSIQ) scores in predicting later academic achievement given significant variability among any of the four WISC-III factor scores. Taken from an archival data set, the sample was composed of 6- to 13-year-old students who were twice evaluated for special education eligibility over approximately a 3-year retest interval. Participants were separated into two groups based on the presence or absence of significant factor score variability and then matched across groups on disability, FSIQ, age, sex, and ethnicity. The results of hierarchical multiple regression analyses indicated that the Full Scale IQ was a valid predictor of academic achievement scores even in the presence of significant factor score variability.