[copied from a recent comment]
Having the teacher hand me a prealgebra textbook and tell me to come back when I had learned it is what happened to me, in 6th grade, with 2 other kids. Add in a summer course of geometry before 8th grade and I was done with Calc BC by 10th grade, at the tender age of 14. During middle and high school I did do the homework, however, although often in the 5 or 10 minutes before class began. This came to bite me in the butt my own freshman year in college, but I perservered, swallowed my pride, and actually began to work for the first time in my life.
Now, a year out of college, I'm in med school. Here I'm surrounded by people who like what they're studying (I do as well), and studying a LOT is the norm. And, at this stage, it actually matters whether I know my stuff, so I put my nose to the grindstone and join in, no matter how much it hurts.
I was quite the academic phenom at a young age (not just in math, I was a SET kid, see http://www.jhu.edu/~gifted/set/ for what that program is about), and this helped me in some ways: I never felt the need to compete in a vicious manner or belittle others' achievements since I'd already had the institutional pat on the back from a young age, so to speak. However, it also made me complacent, and this complacency almost was my failure.
The moral of my rambling, self-congratulatory story? Not everyone who finds the pace and scope of traditional school easy ends up falling by the wayside. We all have to learn how to apply ourselves, and to grasp that being smart is simply not enough on its own. Growing up as a precocious youth one often feels that being gifted means that less effort should be expected of oneself, and that academics is a game in which the goal is to find the least amount of work that will appease the taskmasters. I encourage those who might feel this way to go to a competitive school, and learn from the positive example of their peers that the application of one's talents is as important as their mere existence.