I could not agree more. I had the exact same experience going through school. I would always ask for more work in order to be challenged. I would constantly be looking to do more, because you are correct, school is extremely catered to the average student.
Also, about that quote, because I wrote it, I don't get the readers experience. But looking at it now I can completely get your frustration. I would feel the same thing, since I was frustrated going through school, even though I did fine. I wrote that line as more of a generalization.
"The most successful student in many cases is probably the very average child. Being excessively inquisitive and driven makes the classroom hell, because the system seeks efficiency, and that means punishing the margins for not fitting in with the crowd." This is bang on. Thanks so much for the great comment.