I agree wholeheartedly, CFK. If DS7's test scores hadn't lined up with what his teachers and I had been seeing all along, I wouldn't have trusted them as much as I do.
A 10-point spread might not matter at all. Our 40-point spread was pretty huge, and was very visibly a challenge for us to deal with! No doubt about it!
Dazey: keep in mind that a test score is a snapshot of one moment in time. Sometimes snapshots catch us making a funny face and not looking like ourselves at all. Sometimes they catch us completely as we are. You have to decide what makes sense in your child's case. If the evidence you have doesn't make sense, then you have to get more evidence.
Just don't discount what you see. Scores are one day; your experience with the child is EVERY day!