Today, a dozen years on, Ms. Nemenzo’s debt not only remains, it’s also nearly doubled, with fees and interest, to $33,000. Though Ms. Almendral is repaying the loans herself, her mother continues to pay the price for loans she couldn’t afford: Falling into delinquency on the loans had damaged her credit, making her ineligible to borrow more when it came time for Ms. Almendral’s sister to go to college.

Ms. Nemenzo is not alone. As the cost of college has spiraled ever upward and median family income has fallen, the loan program, called Parent PLUS, has become indispensable for increasing numbers of parents desperate to make their children’s college plans work. Last year the government disbursed $10.6-billion in Parent PLUS loans to just under a million families. Even adjusted for inflation, that’s $6.3-billion more than it disbursed back in 2000, and to nearly twice as many borrowers.

A joint examination by ProPublica and The Chronicle of Higher Education has found that PLUS loans can sometimes hurt the very families they are intended to help: The loans are both remarkably easy to get and nearly impossible to get out from under for families who’ve overreached.