Just out of curiosity - how was the tester able to clearly determine it was interest? I find with my ds that many times when he appears to not be interested it is actually rooted in his learning challenges and resulting anxiety. Unless it's something as totally clear-cut as he's passionate about subject A and totally doesn't care about ever learning about subject B. On testing like this, though, I think it's a real possibility that something that looks like disinterest or disengagement might actually mean there's a hidden struggle there and detaching is the way the student has learned to cope.
The one case she gave that was clearly disinterest was a test where she read a passage out loud, and then asked him questions about it. She did this with two different passages, the first one he was clearly uninterested in and got a very low score. When she did the test with another passage (I think this was normal) and it was subject he was interested it, he did extremely well.
