My experience in school matches that of "The Guy" pretty closely. To this day I still am not quite sure what to make of it; I went to private schools that were probably more challenging than other places I could have been, and I obviously learned a massive amount just being there doing some of the work (to say nothing of the social education), but I just could not make myself care enough to get good grades, especiall…
There's a lot of studies around gifted kids that show that if you praise them for results, they grow up like you (and me), very risk-averse, only applying themselves if they knew they would succeed.
Instead, you should praise kids for effort. Reward work, not just punish non-work, as was done to you.
Even if you're clever, sometimes you just have to sit down and do boring-ass tasks, and it's a very useful adulting skill to have.