Testing anxiety -- work on it. Build tolerance for it. Decoupling the typing from the facts is a great start. That might also explain the AIMSWEB flop. Also, if he's not hitting the reading comprehension (forgive me if I'm projecting based on our experiences), you might also want to work on the math testing from a similar perspective. My DS has not tested well on the internal district testing because the kid has to explain why the answer is right. We've had to teach how to explain that 573 is greater than 462. "Because it's bigger" isn't good enough.
It's hard to avoid being seen as "that mom" when going to a meeting such as that. What has been most successful for me is to focus on the weaknesses. "Can you call me some time this week? I'm wondering about some things I'm seeing in DS' ability to describe what he's read. I'm wondering if you can help me understand his reading comprehension." I then set forward an agenda to talk about the weaknesses. When it comes to the in-person conversation, I think bring up the issues arising from the strengths. My DS has a history of speech therapy and struggles with expressive speech and articulation. It's worked quite well to describe some of the speech history to the teachers as an attempt to have them understand the whole child. Then when the discussion rolls around to the math ("yeah, turns out the school psych had never seen a score that high before...") then I'm not the pushy parent, just the parent looking at the whole kid, warts and all.
YMMV
