WASHINGTON —The federal student-loan program seemed like a great idea back in 1965: Borrow to go to college now, pay it back later when you have a job.

But many borrowers these days are close to flunking out, tripped up by painful real-life lessons in math and economics.

Surging above $1 trillion, U.S. student-loan debt has surpassed credit-card and auto-loan debt. This debt explosion jeopardizes the fragile recovery, increases the burden on taxpayers and possibly sets the stage for a new economic crisis.

With a still-wobbly jobs market, these loans are increasingly hard to pay off. Unable to find work, many students have returned to school, further driving up their indebtedness.

Average student-loan debt recently topped $25,000, up 25 percent in 10 years. And the mushrooming debt has direct implications for taxpayers, since eight in 10 of these loans are government-issued or -guaranteed.

Lifting student debt higher and higher is the escalating cost of attending schools, with tuition increasing far faster than the rate of inflation. And enrollment has been rising for years, a trend that accelerated through the recent recession, fueling even more borrowing.

Mark Zandi, chief economist at Moody's Analytics, argues that government loans and subsidies are not particularly cost-effective for taxpayers because "universities and colleges just raise their tuition. It doesn't improve affordability, and it doesn't make it easier to go to college.

"Of course, it's very hard on the kids who have gone through this, because they're on the hook," Zandi added. "And they're not going to be able to get off the hook."

It's not just young adults who are saddled.

"Parents and the federal government shoulder a substantial part of the post-secondary education bill," said a new report by the Federal Reserve Bank of New York.

And some of the borrowers are baby boomers, near or at retirement age. The Fed research found that Americans 60 and older still owe about $36 billion in student loans.