Lukemac, while these new scores aren't greater than 99.9th percentile, they are far from "fall off a cliff" type scores.. they are still very good! I think there's a very real possibility some of the effect you're seeing is simply that sometimes early testing scores *are* high relative to later scores... or you're seeing a child that has something else going on that's getting in the way of learning.
I'm was curious what his previous test scores were, so I peaked through the old posts... I noticed you had posted about a verbal/reading achievement test score that came in lower than expected earlier this fall (Gates McG? sorry.. forgot the name of the test already)... his scores on that test were 77-85th percentiles... which of course is lower than 99.9th on the WJ-III. Having two sets of lower than expected achievement scores, I'd be tempted to look into what's going on further and not just assume it's boredom with this year's class situation.
I would also wonder about this:
His memory is ridiculous and I almost thought he had that weird memory thing that starts with an I.... And then he bombs the story recall. He could tell you what I was wearing on June 11, 2010! And what song was on the radio....
There are different types of memory, and having a photographic memory for events long ago isn't using the same brain processes that are required to process words read and then remember and/or put together what they meant. I have a dd who has a weakness in associative memory, and she has odd memory blips like what you've mentioned.
polarbear