Originally Posted by kcab
I believe I have read that Wechsler did not intend the test to tease out differences in the upper SDs.
Adding to kcab's post, here's a link to GT-World (seems to be either a precursor to or concurrent project of Hoagies) that includes the quote about Weschler's comment, as well as links to source materials:
http://www.vcbconsulting.com/gtworld/gtwisc.htm

I've also seen this comment copied in various discussions of WISC: "Unfortunately, many psychologists also use the WISC to identify gifted children. This is unfortunate because the test was not designed for such use."

Both of these comments, however, are from the mid to late 1990s (at the latest), before the WISC-IV and certainly before the Extended Norms for the WISC. (And, hoo-boy, the Extended Norms are a whole different can of worms!)

Although I continue to see the quote from Weschler tossed about, I can't really square that up with the broader acceptance of the WISC in the GT-Community, or the high-profile GT specialists's use of the WISC in particular.

(And if it were not a useful test for the upper SDs, why would the DYS program utilize the results?)