[puffythefish]

"But that same kid might naturally pick up the drums and learn to play them for fun, because he can be really good at it."

I don't think the reason a kid may pick it up is so much that "he can be really good at it", but rather because he is "learning to play them for fun". I.e., he's actually interested in it and therefore puts time and effort into it.

With the calculus example, I don't think it's that he's "not naturally talented" (although he may come to believe that), but that he is discouraged/intimidated by his environment. Given enough time and effort, there's no reason he couldn't pick up calculus just as well as the drums; the class simply takes away his passion for it and/or makes it feel like a job.

[bokonist]

Do you really think that everyone has the natural talent to be able to do well at calculus?

but rather because he is "learning to play them for fun"

But what is fun? A person experiences fun when they have a feedback loop of effort, accomplishment, and reward. If you are good at math, you get this from doing math and you find math fun. If you are good at Halo, you get this from beating levels, and playing Halo is fun.