I think that the new extended scoring systems on the WISC-IV and SB5 make this less of an issue (as long as the tester is familiar with them.)
DD tested at 9, and I think her score seems to be an accurate reflection of her abilities. She is not PG, though.
If I were you, I would go ahead and test. The information you get may be useful. If cost is not an issue, there is nothing to be lost by testing, and there is potential gain in terms of insight into your DD's learning style and possibly for advocacy purposes.
I don't think the test will tell you who is "right", but I think it could be useful.
