My son (11) is very good at some things that most kids his age are bad at–such as chores (he does things like taking out the trash without being ask sometimes, and never complains or stalls when asked to do them) and he’s sweet as can be, and is able to have intelligent, mature conversations with adults…
…that said, he has serious problems with school because he doesn’t pay close enough attention. He makes careless mistakes, and doesn’t follow instructions. He doesn’t stay on task. He is very unorganized. He “forgets” to bring homework assignments home. He is very smart, yet gets very bad grades. 
…he is very socially immature around other kids. He still thinks that falling over and making random noises is “funny” the way it was when he was in kindergarten. He babbles endlessly without having anything to say (he’ll actually trail off and then admit that he started a sentence without even knowing what he was going to talk about), and talks about video games all the time despite being told repeatedly that we aren’t interested in hearing it.
…he wants to appear knowledgeable and so he will speak authoritatively about things he doesn’t know anything about. For example, he will say that something “is usually” this or that, when it’s the first time he’s encountered it and has no idea what its characteristics are. He expresses opinion as fact. We’re trying to break him of these habits… “honey it’s ok to speculate, guess, or give an opinion, but you have to say that is what it is. If you say it like you know for sure, it’s a lie and people will stop believing you.”
I also think he may be bipolar, like I am. I’ve seen various hints of things since he was very small, and they really remind me of specific peculiarities I exhibited when I was a child. I’m currently looking for a doctor to discuss this with.
He is really a great kid, though. Especially once you get to know him (he, like many kids, gets into that excitable “show off” hyper mode when he meets people, during which he can leave a bad impression…) He takes care of me when I’m sick, cooks me food, kisses me goodnight. When I get home he will come out and meet me in the garage and will go right to the back door of the car to bring in anything that needs to be carried. And yet he has very few friends. It breaks my heart :,(