Cognitive:
1. The WISC-V has much newer norms than the SBV, which could easily account for 3 or 4 points off the global measure.
2. The SBV does not include measures of processing speed. This makes the best comparison to the SBV global measure the WISC-V GAI--which is only that 4 points lower.
3. The index structure for the SBV is quite different from that of the WISC-V, which makes it more challenging to make direct comparisons cluster to cluster. On the SBV, fluid reasoning is a combination of verbal reasoning (most similar to Similarities on the WISC-V) and nonverbal reasoning (most similar to Matrix Reasoning on the WISC-V). Note that these tasks are in different clusters from each other on the WISC.
There is no quantitative reasoning cluster in the WISC-V core subtests (though one can be calculated, if the supplementary Arithmetic subtest is administered). The closest measure is half of the fluid reasoning index.
Cognitive bottom line: I would say it is not necessary to doubt the validity of either test result on the basis of score difference alone. Anxiety, OTOH, is another story, and could very well have depressed his test performance--but that is likely to show up on the MASC.
Achievement:
1. His WIAT-III results are actually within the range of normal variation predicted based on his VCI (which, as noted previously, is in line with his SBV global measure).
2. Reading comprehension was not assessed, most likely because he is considered a kindergartner, and there are no grade norms for that subtest at that level. He may decode at a higher level in connected text than he does in isolated word reading, as he is able to use his strong language reasoning skills to support accurate decoding. This is a reasonably normal behavior in many high-cognitive early readers.
In general, I find that teachers are more convinced by measures with direct relationship to their curriculum and personal teaching experience--such as performance on placement tests, end-of-course/end-of-unit tests, reading selections that they have used in instruction. Most people more readily accept data that they feel they understand, can interpret independently, and can place contextually.
