My take on introversion and extroversion as a child is this: If I had a reason to talk to you (IE: needed info or the like) I would have no problem coming up and asking a direct, to the point question. If I was forced to talk to you out of simply making conversation, I would hide behind my parents leg, so to speak, or read a book, or bury myself in artwork and semi ignore people, only giving basic responses.
....Pretty much how I still operate. Small talk was as pointless then as it is now to me.
I grew up on a farm, the nearest friends I had were a minimum of 5 miles away, town was about 10. I spent most of my time playing alone, using my imagination, my dad was working two jobs - the one in town, and then came home to do gardening / farming / animal raising stuff. My mom was the same, she had her day job, then all her extra-jobs, working on the church news letter and different things like that. Didn't see either of them in the morning, usually ate supper around 8 or 9 pm.
My mother and I butted heads often, my dad was an avoider (fairly sure he's xxFP, my moms ESTJ). I wasn't terribly emotional, but she could get me to cry, more out of frustration due to her inflexibility to even consider possibility.
I spent most my time either outside in the woods, imagining all the fantasy worlds I read about, elves and goblins and dragons, fighting imaginary figures and having imaginary allies, climbing tree's and such. Or, I was inside, reading books, drawing pictures, making music, building lego's / k'nex.
All of my siblings were 6 or more years older, and pretty much out of the house all the time, so I spent a majority of my time alone. At some point, I got hooked on computers and spent less time outside and more time gaming online, woo dial up playing starcraft, trying to get my mac to be compatible with my friends PC's for games, what few existed other than blizzard games.
At school, I typically didn't get along with any of 'the guys'. I played with girls, or oddball people, like the mentally handicapped children or other socially inept people.
I did a lot of creation and deconstruction of things, figuring out how they worked and making systems and structures on my own, whether it was creating a city in the dirt while playing with toy cars with my mentally handicapped friend, or fixing up my mom's broken gadgets.
That's about all I can remember from my childhood :P
Edit: After reading some other posts, I too was a person who learned the concepts but could never do homework. I only worked on work while I was in school, outside of school, was my time, for me and only me. Nothing would intrude upon that. Aced tests, failed on homework due to incompletes.