I agree that the first thing you need to do is resolve the medical issues. If the thyroid condition could have influenced the testing, then it likely is influencing his behavior at home and school as well. It should be the first thing to be addressed.
After you have addressed the medical issue, then you might want to consider retesting. The testing psychologist did say that he exhibited ADD type behaviors, she didn't diagnosis him, and that seems fair. It sounds like some behaviors did fall in that range. But of course, many things that ID ADD or ADHD also ID a normal kid who is simply exuberent or a gifted kid who is bored or a regular kid who hasn't been taught how to behave (this seems unlikely in your case since you say he is well behaved at school). So, your job is to tease apart what is really what. I think a good test done while his thyroid condition is under control would help you start to figure it out.
I wouldn't jump to the conclusion that you will need a new school. So far it seems like they have been somewhat good about moving him along. You may find that even with a full blown advocacy push they won't challenge him as much as he needs, but until you try (and you will likely need some test scores to move them, but maybe you will find you need achievement type testing and not IQ) you won't really know. Since he is in second grade, maybe you could start with having him take the SCAT test. It was useful to us when we started advocating for our DS last year, and it is quick and not expensive.
You said he agreed to harder work - have you discussed that with the teacher yet?
Cat
