It sounds like your DS would fit into the gifted program based on how he appears in person. I agree that the one subtest score is not going to get him in unless they have a category of qualifying in alternate ways (portfolio for example).
Three things to say. One is medication. I am not personally a proponent of medication for children who are pretty functional, which it sounds like your DS is at home and school. ADHD runs in my family and I have a diagnosis of ADD and I have not found the need for medication. Except when I go bowling. It makes an enormous difference in that one setting, where I can't take back the gutterballs that otherwise spring out of nowhere. So I would just throw out there that if he tries medication beforehand and it has a consistent and useful helpful effect that it may be a way for him to show his strengths on the next IQ test.
In that same vein, a recent study showed ritalin also helped motor skills in children diagnosed with both developmental coordination disorder and ADHD.
http://www.ncbi.nlm.nih.gov/pubmed/23584172 .
It doesn't sound like the neuropsych had any doubts at all about the diagnosis. That he doesn't find the need for meds in day to day life is wonderful, but IQ testing is a very expensive moment in time when he really needs to focus.
Apart from that, it may be helpful to go back to the tester (just you) and discuss more in depth each subtest and how your DS did and what behaviors they showed. The tester probably did not know your DS well enough to be sure they were tanking a subtest while it was happening, there's always the possibility they just are at that level. They also see only the physical types of behaviors that indicate distraction. There's also a whole second level of distraction where performance is impacted without behaviors that whop the tester over the head. So while they said they felt it wasn't representative they may not really get the depth of that. Given that they didn't know at the time exactly where he should have excelled versus what was truly the highest level he was capable of, their comments are only going to help you so much. But it would be useful to know specifically if he gave one word answers in similarities or in picture concepts. Was he getting full points on questions and then just missed a bunch in a row entirely. Or was he giving minimal answers all along. Did he give up entirely on some of the block designs, did he make them inaccurately, or did he take too long?. Did he have a break and then was unable to settle down before the next subtest started? Etc. Get a very long detailed breakdown of exactly what his demeanor was like and exactly how he was responding to questions that lost him points, on every individual subtest. You can learn a lot more from this experience.
We really lucked out with the tester we went to. She turned out to have 3 teenage sons. Therefore not only experienced with hyper boys and the movie/lego characters they know, but also wistful for their younger selves and therefore particularly maternal to cute little boys. She got my DS warmed up to the point of hugging her before ever starting testing. I had told her he needed lots of breaks and she started that way, but after the first one apparently he had trouble settling down enough to begin the next subtest so she intuitively realized not to have him try to change back and forth from focused to running around. In order to get him through the test she let him fiddle with stuff while he was answering questions. It could have backfired with a different kid but she was just that in tune with his needs.
So that brings me to the next issue. Is there a way to make the testing environment better attuned to your DSs needs next time? Maybe one tester is fine for diagnosing ADHD, but for a young child to really continuously put forward their most conceptually perceptive thoughts for over an hour they need a personal connection with the person. Did your DS connect on that level with the tester?
And then other factors. What about doing it over two days... that is allowed for the wisc I believe (not sure about the others), just seldom used by testers because often the test doesn't take very long (for example if the child doesn't score well). But ideally it will take a long time. Are long breaks or short breaks better. Is a snack good or does that just set off a mental rollercoaster. Would it have been better if your DS had met with the tester for an hour a week ahead of time for weeks so they were used to going to their office every Friday at 9 am, is routine or complete novelty better for getting their best performance. What specific things make your DS feel like happily (but not hyper-crazily) expounding on what they know?
And then my last recommendation is practice, and I know there are going to be some that find I'm awfully close to the prepping line here. But I don't mean practicing making patterns with blocks. I mean practicing fundamental test taking skills that come much harder to kids with ADHD.
As an example I would say practice guessing. School does not teach or reward guessing, at school there are specific answer, and the easiest strategy is often to say, "I don't know, what is it." That is also the fastest answer which if you have ADHD makes it attractive. But in an IQ test that is a terrible strategy. Good guessers spend a lot of time thinking about what they know about stuff, maybe say some things to try them out, retract some of it, go slightly but not too far off topic, finally summarize, etc. And that all has to happen in front of a pretty silent audience in a test situation, unlike at home where the parent is a more active listener or even adding in info. So one can practice guessing to a silent audience.
Another thing I wish I had practiced with my DS was just simply not getting to find out the answer right after answering a question. At home and at school often you find out immediately and you are so used to that that not knowing can leave you hanging and unable to move on (at least it does for my DS, who tends to obsess).
Another thing to practice is simply having a timer on for an activity (eating lunch for example, just to get to the point one is not distracted by it). My DS tends to see a timer and try to go extra fast which backfires, but another child might be so lax about a timer they don't really get the idea that it means go fast at the expense of neatness. As a side note if your DS is typically ADHD and distracted by beeping or ticking of any kind you will want to confirm ahead next time about the characteristics of the timer used, and if it beeps or ticks request they get one that does not (it is supposed to be silent).
Another practice item especially for an ADHD type is just practicing at keeping on topic when someone asks a question. Testers may be tightly bound by the rules of what they can and can't say and what type of help they can give, sometimes they may be unable to say "you are getting way off topic here". They are very limited if a child gives an answer to something else: they may not be able to say, "well weren't you supposed to tell me about how bees are similar to books and not insects and books?" There may be a maximum number of times they can remind the child about the rules or aspects of each subtest.
Along the same lines the tester may not be able to repeat the questions in some subtests. For example if it's to test memory then it would be an unfair advantage to repeat it to some kids but not others. If your child has ADHD then they are likely even more used to hearing questions or instructions repeated than other kids, and it may come as a total shock that this time, out of the blue, there is no second chance at hearing the question. It's almost the definition of ADHD that this will be a problem on an IQ test. But it is something you can practice in a fun and reward based way, the skill of listening for very short periods on cue, with no second chance.
I'd summarize but it's gotten so long I can't recall what the beginning was.
