I can speak from experience that any difference between VCI/PRI and PSI/WMI can cause what Dottie and Grinity (and maybe others?) call a "bottleneck." This can cause problems to varying degrees for a child in school. CFK makes a good point, I think.
DS7 has almost a 30-point difference between his PRI and his WMI, and a more than 40-point spread between his PRI and his PSI. (And both WMI and PSI are still above average.)
I always thought of him as a dawdler, and his teachers all commented on it. But once I saw his scores, I realized that that's not fair to him. He's HG+, but his scores mean that he can't hold things in his head and manipulate them much better than an ND child, and he's no faster than an ND child either. This can greatly affect what he's capable of doing. It looks willful, but it's not. He's deep but not fast...and he can't be any faster. He's not GT in the speed department.
However--and I think this is important--I would argue that this sort of "bottleneck" should really be treated as an LD would be, since that's how it plays out for him. Consider a child in the middle of the bell curve with a 100 PRI trying to succeed in school with a 60 PSI and a 70 WMI: he's going to struggle. Now, I don't think the scores translate quite that directly, but I do think that DS7's scores present something of a similar frustration. Adaptations are really called for.
For example, instead of focusing a lot on mental math--which we were doing a lot of before he took the WISC, a strategy that was frustrating for both of us and took SO much time--post-WISC, I started having him write things down. If he can see the math problem and doesn't have to hold so much in his working memory, then he is more capable of using his extensive PRI to solve the problem. It's an adaptation that helps him use what he's got to the best of his ability. We still do some mental math, but it's with the realization that it's not his strength. We spend a little time on it to improve his skills instead of a lot of time on it. Much happier math time is had by all!
Of course, this LD-light approach works better in situations where the teacher is flexible, has some understanding of GTness and IQ tests, and is willing to teach to a child's strengths and build gently upon his/her weaknesses. Not everyone is going to understand that an HG+ child needs both a bigger challenge AND more time to do the problem...
