I was hoping Dottie would chime in with an authoritative explanation of extended norms. (I can't seem to copy the URL and paste it in this message, but you can do a search of earlier posts on this forum, or look under Parents-Testing-WISC-IV at hoagiesgifted.org.) If you can't find it, let me know and I'll see if I can paste the link from Hoagies.
I am by no means a testing expert, but my understanding is as follows:
The short explanation is that 19 is the top scaled score that they give for a subtest. If a child gets a score of 19 they may have answered just enough questions correctly to receive that score, or they may have answered even more questions correctly than are required for a 19. In the latter case, there are now "extended norms" that provide scaled scores of 20 and above. These scores would then feed into the calculation of VCI, PRI, FSIQ and GAI, possibly raising those scores as well.
It's worth checking to see if the psychologist used the extended norms in this case.
