The latest issue of Bloomberg Businessweek features an editorial that would surprise no one familiar with the notion that college has been oversold.

Marco Rubio has done America a great service by offending its chin-scratchers and navel-gazers. “Welders make more money than philosophers,” the senator declared at last Tuesday’s Republican debate. “We need more welders and less philosophers.”

Fact-checkers pointed to the data showing that philosophy professors earn more than welders. But it’s hard to find work as a philosophy professor, and, in any event, Rubio’s essential point is correct: Many jobs for skilled tradespeople pay more than those requiring academic credentials. There just aren’t enough qualified workers to fill them.

Rather than give this shortage the attention it deserves, presidential candidates in both parties have focused on reducing — or in Senator Bernie Sanders’s case, eliminating — the cost of college and its debt burdens. But what about people who don’t want to go to college?

Many skills that are essential to a high-performing economy — and that garner middle-class wages — aren’t taught in college. Welding is just one example. Carpenters, electricians, ironworkers, machinists, masons, mechanics, steamfitters, plasterers, plumbers, technicians of every kind, and many other skilled tradespeople earn incomes that often exceed those for white-collar jobs.

An 18-year old who spends four years as an apprentice plumber might earn $100,000 or more during that span, and avoid paying as much for college. After the apprenticeship, a young plumber can make $50,000 a year, with the prospect of steady income growth: Master plumbers can earn $100,000 to $200,000.

The typical college graduate makes about $60,000 at the peak of his or her career, and is likely to pay about $3,000 a year in loans. And of course, many young people who start college, especially community college, never finish.

Too often, high school students are unaware of these facts and uninformed about training programs in the trades. The shortage of welders alone is expected to be nearly 300,000 by 2020.

To fill this need and improve the prospects of millions of young people, guidance counselors and teachers need to shift their thinking about the skilled trades.