Thanks to a ferocious report from a Senate committee, we now know that the for-profit college industry is a business rife with abuses. Little is spent on instruction, and the most vulnerable people are encouraged to apply by “recruiters” who often use boiler-room sales tactics. Most students drop out, only to find themselves burdened with student debt yet lacking a degree to help them pay for it.

When the report came out, the committee’s Republican minority complained that the panel should have probed traditional nonprofit colleges as well. But trying to cover the vast nonprofit higher-ed sector, which educates something like 90 percent of the Americans who attend college, would have diluted the focus and given unearned legitimacy to outfits mainly interested in making a quick buck.

In a larger sense, though, the Republicans had a point. Some of the same problems the committee uncovered in the for-profit sector are festering in the nonprofit sector as well, even if they’re not as egregious.

Now that Iowa Sen. Tom Harkin’s committee has laid bare the foul deeds of the for-profit sector, perhaps it should shine a light into the hallowed groves of traditional academe.

Some of what it finds won’t be pretty.

In general, traditional colleges are charging more and teaching less compared with decades ago. Students are skating by with less study even as grade inflation keeps their marks up. And there is evidence that many students make little progress.

In one study, nearly half of students tested at 24 schools showed no gain in critical thinking, reasoning or writing in their first two years. More than a third had no gains after four years. But colleges aren’t trying very hard to find out what works and what doesn’t pedagogically.

The most illustrious professors at many campuses spend the least time in the classroom. Many professors teach their own research interests rather than what students need to know.

In technical fields, much of the teaching load falls to badly paid graduate students, some of whom have poor English skills. And at top business and law schools, coursework is too often taught by faculty who never have met a payroll or spent a day in court.

By all these methods, colleges are devaluing their sheepskins and shortchanging their students even as they raise their prices, which have risen faster than inflation for years — fueled in part by the availability of federal student aid.

And too many students fail to graduate. The Organisation for Economic Co-operation and Development, an international think tank, reported in 2010 that the United States had the lowest graduation rate (46 percent) of the 18 countries it surveyed. In part this reflects our success at democratizing college, but it also reflects poor high school preparation and soaring college prices.

All that said, it’s important not to throw the baby out with the bath water. America’s system of higher education is the envy of the world, with good reason. And advanced education is crucial, not just for the health of our economy but for the health of our society. The impulse to have every American complete some higher education is a noble one.

But it cannot succeed unless we reform our campuses to become more efficient as well as more effective, and reform our high schools so that graduates have a strong foundation in reading, writing, math, science, history and critical thinking.

The Harkin committee looked at colleges that profit at the expense of students. Maybe it’s time for him to consider whether the great mass of students are getting enough profit from nonprofit colleges.

Daniel Akst is a columnist for Newsday and a member of the newspaper’s editorial board.