"What percent of jobs in the economy need more than reading, writing, arithmetic, and apprenticeship?"

My Dad lost his welding job around when I was starting high school. He took a few different jobs, one of which was cutting brush with a machete for a local private surveyor. He found the surveying work interesting, so he checked out books from the library to re-learn his Trigonometry (and probably a few other things). This allowed him to get a job with the Pennsylvania Dept. of Transportation surveying group, from which he took early retirement a couple of years ago. I think having an initial exposure to Trig in high school allowed him to realize this career change was possible.

So, it is hard to say what knowledge will be useful, or not, over the course of a lifetime.