The true return to college heavily depends on the probability of successful completion.  That probability in turn heavily depends on pre-college academic performance.  How heavily?  Check out these three graphs from Bound, Lovenheim, and Turner’s “Why Have College Completion Rates Declined?” (American Economic Journal 2010).  BLT compare results for the NLS72 (high school graduation cohort of 1972) and NELS:88 (high school graduation cohort of 1992), using a standardized high school math test to measure pre-college performance.

First, check out your probability of trying college if you finish high school.

Notice: By 1992, college is the default choice for most of the achievement distribution.  Almost half of high school grads in the lowest quartile of math performance – and two-thirds in the second-lowest quartile – try college.

Next, look at the probability of finishing college if you try college.  To get credit for finishing college, you have to graduate within eight years of
your cohort high school graduation.  For the class of 1972, that’s 1980;
for the class of 1992, that’s 2000.

Probability
of success for the bottom half of the distribution started low in
absolute terms: about one-quarter for the bottom quartile, and one-third
for the second quartile.  Over time, though, the bottom’s success rates have gone from worse to awful: Barely 10% of those who try college manage to
get over the finish line.

Last, let’s multiply the preceding probabilities together to get the the probability of finishing college if you finish high school.

Notice: Although kids in the bottom quartile became much more likely to try college, they became no more likely to finish.  The fruits of effort for the second quartile are also underwhelming.  How can this be?  Because the probability of finishing college if you try college actually fell for the bottom three-quarters of the distribution!  This is the fruit of America’s
college-for-all mania
.

Will I tell my kids to go to college?  Sure.  Does this make me a big hypocrite?  Not at all.  I shall follow the same principle I commend to others: Encourage high academic achievers to go to college, and urge the rest to do something else.  More specifically: Push college for the top quartile, tolerate it for the third, discourage if for the second, and decry it for the first.

To be clear, this is prudential advice aimed at individual students, not a public policy recommendation.  From a social point of view, I’d only push college on the top 5%.  Unless, of course, the student loves learning enough to attend classes unofficially.  The more of these rare unicorns on campus, the merrier.