English language proficiency and tests of intelligence and academic achievement

The present study examined the relationship between English language proficiency and tests of academic achievement and intelligence. Preliminary evidence suggests that language proficiency influences academic achievement and intelligence test scores, but language proficiency generally has been inadequately measured. The study was designed to (a) determine if English language proficiency would predict intelligence and academic achievement test scores and (b) find a model of the factors underlying language proficiency, intelligence and achievement test scores that provides good fit with the data. A sample of Hispanic children referred for a psychoeducational evaluation to assess for the presence of a learning disability was administered the Wechsler Intelligence Scale for Children-Third Edition (WISC-III), the Wechsler Individual Achievement Test-Second Edition (WIAT-II), and the Woodcock-Munoz Language Survey (WMLS) in English. Multiple regression procedures revealed WMLS Oral Language subscale scores were a significant predictor of WISC-III Verbal IQ. In addition, WMLS Reading-Writing subscale scores were a significant predictor of WIAT-II Reading Composite scores. Confirmatory factor analyses were conducted to examine the factor structure underlying the English language proficiency, reading achievement and Verbal Comprehension subtests. A two factor model in which the Reading-Writing subscale of the WMLS loaded with the three WIAT-II reading subtests and the Oral Language subscale of the WMLS loaded with the four WISC-III verbal subtests resulted in the best fit to the data of the models specified, although the fit could only be described as “fair.” Separate confirmatory factor analyses were conducted to evaluate the factor structure underlying English language proficiency, Performance IQ and math achievement. A three-factor model with correlated factors resulted in a good fit to the data. Findings of the study suggest practitioners should be cautious in interpreting results from all three measures. In particular, the WMLS should not be viewed as a pure measure of language proficiency and the effect of language proficiency on IQ scores, even with relatively proficient English speakers, should be considered.