I'm a teacher, and this is one of the things that frustrates me deeply about our education system. I welcome students like this; they're so much fun to work with. But I usually have to make them feel accepted before I can begin to work with them. I teach in a small alternative high school, and by the time bright students get to me, they're often used to being shut down for picking things up quickly and not having to do homework.
I met a really bright and interesting guy once who told me about his experience in first grade. His teacher gave everyone a math workbook, and he was really excited to be learning math. He finished the workbook in a day or two, and excitedly brought it to his teacher, expecting to be given another workbook. Instead she glared at him and said something along the lines of, "I can't believe you cheated on your math workbook in first grade!" She gave him another copy of the same workbook and told him to do start over, and that she'd be watching him. He thought to himself, "Well that sucked, but she'll watch me do it this time and know I can do it." So he did, but this time she just got mad at him and said something like, "I don't have anything else for you to do, so here's another copy of the workbook. Don't finish this so quickly."
He learned what so many bright kids learn: if you learn things too quickly and speak up, you'll just make the adults around you mad and they'll give you more meaningless work to do. I know there are many teachers who handle bright kids really well, but as a system we fail many kids. These effects last years, and often times decades.