The GAI takes out the timed, more physical aspects of the WISC-IV. The WISC is usually the test of choice for school systems because it helps educators know who is having processing - either physical or intellectual - weaknesses that make it hard for the student to show what he or she knows and what the child might need some therapy or special provisions to deal with. In other words, if a highly gifted child scores within the average (normal) range on those parts, it is simply normal. At the same time, it can pull down the intellectual score, which is why the GAI was devised. Some HG+ kids are also high on those GAI-omitted subtests, though, and they will indeed have an edge over those who aren't, e.g. they can press a buzzer faster on Jeopardy:-) So, I tell my clients that Abbreviated Battery scores on the SB5 or the GAI on the WISC-IV are helpful for underscoring the intellectual "essence" of a child, but the un-prorated scores help us to understand "holes" in the profile, places where we are sometimes surprised that our brilliant child can't do it or performs less well than expected.
It is complex. What really matters is whether or not the person who evaluated your child can help you to understand and offer appropriate support for him or her. Ultimately, scores are not the issue. They are merely samples - samplings - of how your child reasons and thinks. The goal, after all, is to do what we can to facilitate the child's growing into the fulfilled, independent, emotionally sound person he or she was designed to be. When my children were younger, I focused on scores, too. It is natural, I think, to do so. But eventually, as they grew and matured and did what they wanted to do, I finally learned what it a joy it is to simply watch what they do, who they are, and where they are going still. Getting the scores right ended up not to make much difference at all.
