I don't think I'd make a diagnosis of developmental coordination disorder on a BD of 10 when Coding was also 13 (in the context of a Symbol Search of 13 also, indicating that graphomotor was likely not slowing the kid down all that much. I'd have to know a *lot* more about the situation, of course.
I agree that the tester should have calculated the GAI, and should also definitely have explained about which of those differences are statistically significant and how common they are in the average and the high-IQ population. That's easy stuff and (other than the GAI, which is for free on the Harcourt website) is in the manual.
Grade equivalent scores, even on a continuously-normed test like the WJ, don't mean half of what you think they mean. I don't report them when I have the choice not to. What I report instead (given that the WJ provides them!) are Relative Proficiency Index scores, and Generalized Relative Proficiency Index scores, which are considerably more statistically defensible and let me make the same case. In terms of recommending specific academic placement, that has to be done on the basis of criterion-referenced information and comparisons to the actual curriculum.
I don't think you need a retest, though -- would be more useful and less expensive to either (1) get the original tester to do what you paid her to do (should cost you nothing) (2) have an expert get copies of the protocols from the original tester and do a second-opinion consultation for you.
