People should be apprenticed at 13, and should enter professions at about 18. Only jobs requiring memorization of a large body of prior work (medicine or science) need more than that.
But... I strongly believe that a reasonably bright and literate high school sophomore could absolutely begin law school. On average, they probably wouldn't do as well as they would after college, because your writing, reading comprehension, and exam taking skills do improve in college.
But I actually think people would be very surprised with how strong a performance smart 15 year olds would show. I'm not talking genuises here, just pretty smart kids.
I think it's simply a matter of human nature; given too much leisure, or too high a quality of life, our brains will still be physiologically unable to feel a proportional level of happiness. At the chemical level, there are only so many neurotransmitters to go around.
Anyway, the point of all this is that I would have been thrilled to get a "real" job at that age, but I'm not sure that was right. I was always very much in a hurry to finish school, and now that I have a job and am in college early, I keep wondering if, and feeling like, I've made a terrible mistake.
And a separate point about the article: The cost of college is almost entirely the fact that it uses up the four most productive years of your life. That most people choose college almost on instinct surprises me. Forget buying a house or a car - this decision is orders of magnitude more expensive. If you want to have an extraordinary life, you're going to be on that path by the time you're 22, or you're not. It's worth noting that Einstein made his contributions to physics at the age of 25, and even that was somewhat old to develop something so innovative. At the same time, while he stayed influential and productive in physics, he never published anything as revolutionary. At a certain age - I'm inclined to think it's usually in the early to mid twenties, based on anecdotal evidence only - you just lose that ability. If you go to college, you're basically saying "I'll trade my ability to change the world for a predictable life." And honestly, right now that's a trade I would like to make, but I'm just not doing it, and I don't know why.
And besides, every time I put this in writing I am struck by the incredible level of arrogance and hubris in my words (I'm no freaking Einstein!) and I really don't feel like writing again for a long time.
In the US, someone can spend all of high school in auto shop, and still have a chance of changing directions and ending up with a successful career at 33 that some bureaucrat never would never have predicted 20 years earlier. If may take him longer than the kid whose parents and teachers were guiding them towards medicine or business from age 13, but the doors are open.
I think this is a strength of the US, both economically, and with respect to various liberal, democratic, egalitarian ideals. It isn't perfect though. There are certainly people would be happier and better off if they started learning a trade at an earlier age.