As American families refresh the wait lists and weigh their aid offers, yet another cohort of children sets foot into our disaster of a national higher education financing system. Student debt in the United States is over $1.5 trillion, with half of it accumulated in the past decade. Income share agreements — in which borrowers pledge a percentage of future income against debt — present the first plausible alternative. That’s what we should be afraid of.

There’s a lot to dislike about the student debt status quo, which is now almost completely controlled by the federal government. Although the Democrats don’t like to talk about it, the Obama administration effectively nationalized a vast majority of student borrowing in 2010 when it ended federal guarantees for outside lenders as a cost-cutting provision of the Affordable Care Act. The government has a number of advantages as a lender, including an exemption from regulations on debt collectors and the ability to print money. Private investors have thus been pushed to the margin of what has become the largest nonmortgage debt category in the United States; the federal government has over 90 percent of the market.

Income share agreements, or I.S.A.s, began as an experimental model of education funding. One of the first income share programs was designed in the 1970s with the help of the Nobel Prize-winning economist James Tobin at Yale. It was poorly structured in a number of ways — students signed on as a class and kept paying until the whole debt was gone, but wealthier graduates who were able to pay a large chunk at once could opt out — and it closed down (without full repayment) in 2001. One big problem with I.S.A.s is that there is no collateral to these loans. You can’t repossess a classics degree. And as Gary Becker, the University of Chicago neoliberal economist, once lamented, “courts have frowned on contracts which even indirectly suggest involuntary servitude.”

Purdue and a few other universities have come up with I.S.A. programs that could point the way forward. They assess different rates and repayment durations depending on the borrower’s major. If you’re a chemical engineering major at Purdue, you enjoy better terms than if you study English: Under its I.S.A. schedule, chemical engineers are expected to repay $33,000 at the rate of about 8.5 percent of their income for seven years and four months, while for English majors it’s almost 15 percent for nine years and eight months. But these university I.S.A.s are meant to supplement rather than replace student loans.