Thanks guys!
I had never considered my son could have issues with visual processing. I don't even know exactly what that would be.
The psychologist did think that he has difficulty planning, and that that could be affecting his picture concepts, perhaps -- whichever test had him copying diagrams; but he still scored average or high average there.
I guess what has me confused is that 19 score in comprehension. The psychologist really went on a bit about that. She said that that particular subtest was highly correlated with future achievement. I can't remember exactly what she said it measured, but she said that it wasn't influenced so much by background knowledge itself,but the child's ability to make sense of the world, general principles, and to express himself. She said that he hit the cceiling on this test.
She said stuff like "Dinner conversations at your house must be fasicinating", that he had the mind to be a PhD in philosophy, literature, etc; and that she wasn't sure that the TAG center school we have him enrolled at as was enough to keep up with his needs for more exposure and satisfy his need for inquiry.
The thing is, dinner table conversations at our house with him aren't anything special. He doesn't seem all that bright to me, frankly. He can't stay on one topic for long before he just gets bored and checks out. He'll ask a question, but if you try to explain something to him and it doesn't satisfy him immediately, he almost walks away (or at least checks out of the conevrsation). Or he annoys his sister, or blurts out a stupidly annoying fart joke.
On the other hand, over the past years I've had some interesting comments from our friends who talk with him at family parties. Both my husband and I were extremely good students, went to top colleges, and out friends have advanced degrees also from top colleges and went to some of the best schools in the country -- and they have smart kids, too. Twice, this year, my friends have sat and engaged my son in a longish (for him) conversation on some topic and have come to tell me, "You have a very bright son there". I honestly just roll my eyes a bit (inwardly) because I just don't see it myself.
I see him as slightly smarter than the average 4th grader; with very poor work ethic; little empathy for others; a lot of difficulty writing; gives up at the slightest hint of difficulty; explodes when he is frustrated (though that is getting better).
And I can't image what the psychologist thinks I should do with him aside from sending him to the TAG center school. It is already a challenge for him to get decent grades there because of the lack of paying attention to details and handing homework in on time!