I combine a regression discontinuity design with rich data on academic and labor market outcomes for a large sample of Florida students to estimate the returns to college admission for academically marginal students. Students with grades just above a threshold for admissions eligibility at a large public university in Florida are much more likely to attend any university than below-threshold students. The marginal admission yields earnings gains of 22% between 8 and 14 years after high school completion. These gains outstrip the costs of college attendance, and they are largest for male students and free-lunch recipients.
Here is the Journal of Labor Economics piece by Seth D. Zimmerman. So is the non-statistically-summarized account of Susan Dynarski painting too negative a picture?
And do those people need debt forgiveness to the tune of hundreds of billions of dollars? Write down your social welfare function!
This piece by David J. Deming surveys the broader literature, and with broadly concordant results.