Well, I guess in part it depends upon how you define "well-rounded." But many kids are curious about virtually everything and would be extremely well-rounded if allowed to pursue what crosses their paths, especially if the parents expose them to lots. There really are a lot of people who like to learn a little about everything.
Mmkay. What, like 40%? What percentage of these naturally well-rounded kids would prefer to study everything-- the social studies, the math, everything? I'm curious to know how high the percentage of kids who just
naturally like social studies is, in your estimation. Then I would certainly like to know the basis of your estimate.
Keep in mind that any non-negligible number of kids who aren't well-rounded by nature means the scheme won't work well at all. So you basically must be assuming that nearly everyone is "extremely well rounded" by nature.
Also, learning a little about everything doesn't cut it. That would pass kids who go off to college knowing only first-grade-level math. That's why competency standards exist; we can't leave things to assumptions and kids liking to know a little about everything.