It’s dismaying how easy it is to screw up college.

I don’t know exactly when, why, or how it happened, but important things are breaking down in the US higher education system. Whether or not this system is in danger of collapsing it feels like it’s losing its way, and failing in its mission of developing the citizens and workers we need in the 21st century.

This mission clearly includes getting students to graduate, yet only a bit more than half of all US students enrolled in four-year colleges and universities complete their degrees within six years, and only 29% who start two year degrees finish them within three years. America is last in graduation rate among 18 countries assessed in 2010 by the OECD. Things used to be better; in the late 1960s, nearly half of all college students got done in four years.

Have graduates learned a lot? In too many cases, apparently not. One of the strongest bodies of evidence I’ve come across showing that students aren’t acquiring many academic skills is work done by sociologists Richard Arum and Josipa Roksa and summarized in their book Academically Adrift: Limited Learning on College Campuses and subsequent research.

Arum, Roksa, and their colleagues tracked more than 2300 students enrolled full time in four-year degree programs at a range of American colleges and universities. Their findings are alarming: 45% of students demonstrate no significant improvement on a written test of critical thinking called the Collegiate Learning Assessment (CLA) after two years of college, and 36% improved not at all after four years. And the average improvement on the test after four years was quite small.

Consider a student who scored at the 50% percentile as a freshman. If he experienced average improvement over four years of college, then went back and took the test again with another group of incoming freshmen, he would score only in the 68th percentile. The CLA is so new that we don’t know if these gains were bigger in the past, but previous research using other tests indicates that they were, and that only a few decades ago the average college student learned a great deal between freshman and senior years.

These declines in learning and graduation rates come during a time of exploding costs. the Pew Research Center found that the price of a private college education tripled between 1980 and 2010, and that average student loan debt for bachelor’s degree holders who had to borrow was more than $23,000 in 2011. This debt is not dischargeable even in bankruptcy, and is certainly not erased if you fail to graduate.

Smart students from affluent homes and elite colleges and universities continue to do really well, but the rest of higher ed is sliding backward. Why is this? As was the case with the sub-prime crisis and subsequent economic meltdown, there is plenty of blame to go around. Many non-elite colleges have seen their enrollments jump in recent decades without similar increases in budgets, so resources per student have declined.

It also seems, though, that colleges in general have stopped asking students to work as hard, and the students have been more than happy to take them up on that offer. Arum, Roksa, and their colleagues document that college students today spend only 9% of their time studying (compared to 51% on “socializing, recreating, and other”), much less than in previous decades, and that only 42% reported having taken a class the previous semester that required them to read at least 40 pages a week and write at least 20 pages total. They write that “The portrayal of higher education emerging from [this research] is one of an institution focused more on social than academic experiences. Students spend very little time studying, and professors rarely demand much from them in terms of reading and writing.”

Here’s my advice to recent high school grads (and their families): don’t be part of this shameful and lazy bargain. Resolve to work hard, take tough classes, and graduate on time. Many changes are necessary in higher ed, most of which will take a great deal of time. But the most effective interventions can start the day you show up on campus. Crack the books, find good teachers, and take the education part of your education seriously.

Arum and Roksa found that at every college studied some students show great improvement on the CLA. In general, these are students who spent more time studying (especially studying alone), took courses with more required reading and writing, and had more demanding faculty. So the blueprint is here. Please take my advice and spend some time this summer thinking about how you’ll put it into action.