eco, yes, that makes sense. All new tests show a tendency for scores to drop on students who are being re-tested (the Flynn effect), due to norm obsolescence of the old version, with some research finding the drop to be greater for those at the right end of the bell curve.
The WISC-IV was not re-normed, but the WISC-IV norms were over a decade newer than those of the WISC-III (just as the V's norms are over a decade newer than those of the IV).
I find the WISC-V to have better-defined indices as well. Notably, breaking the old PRI into the Fluid Reasoning Index and the Visual Spatial Index. Working Memory also now has both visual and auditory tasks (and an optional Auditory Working Memory Index).
