This community seems an intelligent bunch.
When people find out what I do it's inevitable that they will start to tell me at some point "I know this person who is an incredibly talented musician..." And I stop them there by saying "Musical talent is pretty much the least part of this." (See: GWAR, Insane Clown Posse, et. all.)
The guy who graduated HS one rank above me, would joke that we were not the smartest two people in the school, we were just the two with the worst social lives.
So I don't think it's about intelligence at all, it's about doing the work, day in and day out. It's about not going to the dance because you were going to the library instead, or not going out to the movies with the gang, because you were home doing extra-credit work, which was stupid, 'cause you already had the highest grade in the class. But if there was extra-credit work, we'd both be doing it. The bands I worked with/for used to call me "Poindexter" because I'd have my books with me at all times, and as soon as I was done working, I sit down and start studying. I'd have to gently remind them that Poindexter could fix their amps and build F/X pedals for them, and they could not. (Poindexter was also getting paid no matter if the band was or not - a whole different level of intelligence in action there). My one saving grace was that I was in love with the smartest (who was also the kinkiest, funny how those two go together) girl at the girls school who thought that sex was the best - and really the only acceptable - study break. She took me shopping for my first dress as a reward for my SAT score (the language section, the math section, not so much).
Point is that grades are not a reflection of intelligence as much as they reflect the time+effort you put in to get them. Scholarships and such also take into account 'outside activities' so my academic advisor (the girls called him Father Whatawaste) made sure I did all that 'resume' stuff. So I ran for class office and student body offices, not because I gave a rat's ass about student government - I didn't - but because they looked good on my resume. I did the student manager/trainer deal for football and basketball, not because I cared, but because they looked good on my resume.* I did the yearbook thing, not because.... Well you get the picture.
* - it also guaranteed me straight As in PE, because the gym teacher was also The Coach, which otherwise would have been low Cs, at best. And, at that, I rarely did PE, always having to 'do something' with the manager/trainer stuff - which usually amounted to locking myself in the trainers room or the equipment room and studying. This turned into a huge fight my senior year with the parents of three students - all of whom were a lot smarter than I was, I'll cop to that - and who, if the PE grade was tossed, would have all had higher GPAs than I did, and who by some 'right' should have been salutatorian instead of me. My thinking was, and still is, that finding a way to get an A in PE without having to get all hot and sweaty, shower with everyone else and get pegged in the face day in and day out in dodgeball did make me a bit smarter in a 'real world' way, even if my academics were not.