Is it possible that the child just found one section of the test really dull? I have seen that with DS, where he will do better on something with the right amount of challenge and then check out for the easy stuff, so there looks like a big difference even if there isn't.
But if the difference is real, then it seems like it would cause a problem even if the lower score is in the normal range. I think DH has something like this going on and you can almost see how one part of the brain can't keep up witht he other adn he gets so frustrated. We've joked that it's like putting a jet engine on a Toyota. Both the jet engine and the Toyota are just fine in the right context, but they are going to have some trouble working together.
