“Learning is its own reward.”

Nineteenth century English essayist William Hazlett was right about that.

But in 21st century America, lots of college graduates have learned the hard way that their degrees didn’t reward them with a good job — or maybe even any job.

Once upon an earlier time, a college degree carried considerable weight with prospective employers.

Not anymore. Too many companies have found that too many college graduates’ skills lag far below their grade-inflated academic credentials.

So as Monday’s Wall Street Journal reported, next spring seniors at about 200 U.S. colleges will take the “Collegiate Learning Assessment” test, which “aims to cut through grade-point averages and judge students’ real value to employers.”

According to the story, the SAT-like exam “represents the latest threat to the fraying monopoly that traditional four-year colleges have enjoyed in defining what it means to be well educated.”

Michael Poliakoff, vice president of policy for the American Council of Trustees and Alumni, explained: “For too long, colleges and universities have said to the American public, to students and their parents, ‘Trust us, we’re professional. If we say that you’re learning and we give you a diploma it means you’re prepared.’ But that’s not true.”

This much, however, is painfully true:

The rises in grade-point averages, tuition and student debt have been accompanied by a decline in a college degree’s job-market stock.

And for recent college grads, that’s an expensive learning experience.