At school I was probably similar, and thinking back basically an awful child, for much of the same reasons. But at least in some of my classes (maths, for example) they recognised that just following the standard course at the same pace as everyone else was a waste of my time, and allowed me to work on the course material for the next years classes, which was at least a little more interesting, and some kind of extra-curricular maths problems as part of an inter-school competition that were much more interesting.
OT - the maths problems didn't always hold my interest, and when I couldn't be bothered doing the actual work of proving something rigorously, I instead wrote a brute-force solver in PASCAL, that produced the correct solution. Then I had the challenging task of persuading people that this was actually an acceptable method of solving a problem. I can't remember if I succeeded, but I think I gave the example of the computer proof of the four-colour theorem that I had read about in New Scientist.