I agree with aeh, his scores aren't atypical for a highly academic child. Executive functioning (in which processing speed plays a role) correlates more strongly with academic performance than overall IQ...so according to his profile (higher PSI, lower GAI), your child is more likely to do well academically than if the scores were reversed (higher GAI, lower PSI). Additionally, your child's VCI/FRI/VSI fall in what's often considered a sweet spot of IQ.
All that said, I wouldn't assume this to be an underrepresentation of his abilities. For the most part, it's more or less consistent. And, the majority of children tested (including those used for the norms) aren't perfect examinees, sitting still in their seat and giving their absolute best throughout the tests with zero frustration...they're kids, after all. A good examiner can generally pull out adequate answers from a child even if the child is a handful.
