The WIAT-III can be used with the age-appropriate Wechsler cognitive scales as well as the Wechsler Non-Verbal Scale of Ability and the Differential Ability Scales – II. Integrating the subtest standard scores and composite scores of the WIAT-III with the WISC-IV provides for above average reliability scores ranging from good (.83-.89) to excellent (.90-.97). Therefore, with Mississippi’s reliance on a discrepancy diagnosis for Specific Learning Disability, comparisons between cognitive ability and achievement are good to excellent.
Behavioral observations across cognitive and achievement testing can yield important information. Look for behavior that is stable and that changes in the areas of affect, motivation, and self-confidence as well as changes in behavior based on the types of tasks administered.
As mentioned above, MDE allows Psychometrists and School Psychologists to use an achievement-ability discrepancy to diagnose Specific Learning Disability. However, legislation passed in 2004 (PL 108-446) does not require diagnosticians to use this traditional discrepancy model. Other models may be used including RTI. Additional models may include the Modern Operational Model of SLD, the Concordance-Discordance Model of SLD, known as the Pattern of Strengths and Weaknesses (PSW) Discrepancy Model. As you may surmise, there is much discussion and disagreement in the area of diagnosing SLD.
When testing children with ADHD, achievement scores may be 20-30 standard score points lower in reading, reading comprehension, and math. There is usually co-morbidity with the SLD and ADHD. Students with ADHD are more likely to be served in SPED.