chemistry, physics, calculus, algebra, geometry, statistics, computers, shop, gym, literature, english, psychology, biology, law, history, second language, philosophy, economics, geography, civilization, environmental science, government/politics, world studies, home economics, engineering, fine arts, graphic design, programming.
everything's an opportunity cost, and many skills interfere and even conflict with other skills. my question to you is this: how many of your adult friends don't know how to cook dinner for themselves? How many can't manage their own finances? How many can't build a shelf for their bedroom or a set of cubbies for their children? How many can't clean their own homes? How many can't read a weather map, understand a shakespeare play, or convert between basic units of measure? How many don't know where hawaii is, how to plug in a computer, or count the first ten prime numbers?
Everything has merit and value. That's never the point. You're not learning "everything". The question is what has relative merit and value. And what you'll find is that those people who've been taught the most, can't keep most of it straight enough to use it at all.
A simple blue-collar never-learned-anything-but-a-hammer-and-a-screw-driver can build just about anything small in his home. All by himself, on a whim, quickly. Furniture, shelves, decks, christmas decorations, you name it. The guy who spent thirty years in school, including shop classes, has far more money in his pocket, and far fewer shelves in his home. So he hires the first guy to make things. The first guy is always happy, except when he's short on money. The second guy is always stressed, despite having money.
I was the second guy. It's taken me five years, but now I'm much closer to the first guy. It'll take me another few years of "learning", but I'll get there.