There is significant debate over the value and ethics of IQ testing for children, including those from diverse cultural groups, particularly in light of studies examining performance on various subtests that are uncovering important processing differences between cultural and linguistic groups (Sotelo-Dynega, Ortiz, Flanagan, & Chaplin, 2013). Whereas the predictive validity of IQ has been well established, the link between general intelligence and general academic achievement remains unenlightening, particularly with respect to educational interventions and remediation of academic skills. In light of the importance of understanding the needs of diverse groups within educational and instructional settings, the present study investigated the differential predictive validity of WISC-IV, Full Scale IQ, Index, and subtest scores for components of reading achievement for European American, African American, and Latino American children. Using data from the WISC-IV-WIAT-II standardization sample, Full-Scale IQ, Index, and subtest scores were used to predict Word Reading and Reading Comprehension scores on the Wechsler Individual Achievement Test, Second Edition (WIAT-II) using forced-entry multiple regression analyses. In general, the results emphasized the importance of subtest analysis for understanding the nature of reading performance of all cultural groups. The amount of variance lost moving from subtest to Full Scale scores is greater in the African American group than the European American or Latino American groups. The amount of variance in components of reading performance accounted for by the Full Scale IQ differed amongst these groups. Findings are discussed in terms of the differences in the processes used in reading between these groups and point to the need for differentiated instruction and intervention to improve reading performance.