If we compare the WJIII Verbal and Thinking clusters to the WISC-IV GAI, the difference is notable, but not as shocking. Cognitive Efficiency, however is substantially lower than the others; this cluster contains the equivalent of the WMI (Numbers Reversed, similar to Digit Span) and PSI (Visual Matching--closest to Symbol Search) scores, with both subtests comparable to about an 8 on the WISC-IV.
Verbal Ability is more-or-less equivalent to the WISC-IV VCI, with the component tasks most like WISC vocabulary and similarities.
Thinking includes the WISC PRI-type tasks (Spatial Relations--closest to a motor-free version of Block Design--or the Visual Puzzles on WISC-V, and Concept Formation--fluid reasoning task, though not much like Matrix Reasoning), and some others (long-term memory, auditory processing). Because it's such a mixed measure, with skills not covered by the WISC, our ability to compare to any specific portion of the WISC is limited. And we would need the extended version of the test (twice as many subtests) to have meaningful cluster information that separates these skills.
The reason she administered this test is quite simple, actually: he had the WISC-IV last fall, and the minimum re-test interval is 24 months. Therefore she had no choice but to give something other than the WISC, and this is what she had available. Can't speak to the part about being not an acceptable instrument under state policy! Of course, what would have made more sense would have been to accept the WISC results for purposes of SSA determination, and skip the re-test altogether.
