You just described my son at that age. First initial and all. Eveyr time he came with me to the conveninece store, ppl would comment how if I could bottle his energy and sell it I'd be a gozillionaire!
Ah, yeah. I said that too about my son. And daughter if you recall? But guess what? Both are diagnosed with Asperger's syndrome - a form of autism. Meeting either for the first time, you'd never know it. What makes you think that? Because it doesn't fit the diagnosis you think should belong? What really struck me is what you had just posted about the teacher's report where J doesn't seem to respect the rules of life in a group. Sounds like a deficiency in social skills.
Life is funny that way, isn't it? It's all a journey and I guess we need to be flexible and open to different possibilities.