It may actually be that his test papers got mixed up with another student. If not, then the processing speed may be a factor. Is wait time also in his IEP, or is the IEP only for gifted? The teacher's account and your DC's account are consistent with each other in suggesting that she assumed that a correct response would necessarily occur within a certain time frame. Since she brought this up herself, perhaps that would be a good connection point to mention to her that he likes to take his time thinking carefully before he answers, so waiting an extra beat or two can be very worthwhile with him. On his part, eventually it will be valuable for him to learn to advocate for processing time for himself, both by explicitly asking for more time to think, and implicitly, by learning some cue words that signal thinking, instead of sitting in silence. (E.g., repeating/restating all or portions of the question, "hm," "let me think about that," "give me a moment," touching his temple or chin to signal thinking.)
aeh - it just occurred to me that DS may already be doing this and I have been discouraging it. Hmm. I do a lot of math work with him and over the past year or so he's developed a habit of asking me to repeat the question "Wait, what?" he will say, though I ask him not to do it because I have figured out he does know what I asked. I perceived this as slowing him down, but maybe it was his defense to feeling like he didn't have enough time?
I think something like restating the question would be more constructive though. "Wait, what?" was driving me crazy and I can't imagine his teachers would enjoy that either.
