oops - forgot to say, that I expect only Davidson knows the answer to the above and you probably will want to ask them (e.g., how can you prove reading comprehension?). And in answer to Dottie's point, I'd guess (and that's a guess) that the reason they are "only" asking for evidence of academic achievement 2-3 grades ahead is because your DS already has qualifying verbal scores. Seems to me that they are looking for confirmation that his academic output will catch up to his verbal reasoning ability. And per their portfolio information, they do accept audio and video.
