Democrats vying for the White House are promoting an unusual way to slash the cost of college for millions of American students: invest in day care.

Slightly more than a quarter of undergraduates in the United States are raising children. That’s about 4.8 million degree-seekers who have another mouth to feed between classes. Advocates say a little-discussed portion of Hillary Rodham Clinton’s new plan to make college more affordable, the latest design from liberal lawmakers to shrink student debt, could help them graduate with a lighter burden.

Under Clinton’s proposal, schools could receive special grants if they pour more resources into campus child care.

The New College Compact, unveiled Monday, comes as leaders on the left call for “debt free” college, a concept embraced by Clinton’s challengers. In May, Sen. Bernie Sanders (I-Vt.) announced his intention to push for “free tuition.” Former Maryland governor Martin O’Malley, who released a similar plan, called cheaper campus day care “a first priority.”

This kind of action is particularly urgent as more students with young children are entering college, said Lindsey Reichlin, a research associate at the Institute for Women’s Policy Research. Many begin freshman year with more family responsibilities than, say, plans to attend fraternity parties.

“It’s an invisible population,” Reichlin said. “Most universities aren’t aware of the parents on their own campuses. It’s easy to associate college with young adults who still receive support from their parents. But a large share of students with kids are low income, and they’re making extreme sacrifices to get through school.”

These challenges spur some to delay their education or quit school. Fifty-nine percent of a sample of Mississippi mothers who dropped out of community colleges told researchers that access to more stable, affordable child care would have helped them stay in school.

Women make up 71 percent of the national student-parent population, often juggling college and parenthood without the support of a partner, the IWPR found. Forty-three percent are single mothers, and 11 percent are single fathers. Data from the 2008 Community College Survey of Student Engagement shows there’s little time for sleep between studying and parenting:

The prevalence of parenting on campus varies across racial lines. Nearly half of black women in college have dependent children, followed by 41 percent of American Indians or Alaska Natives, and 39 percent of Native Hawaiian or Pacific Islander women, according to the IWPR.

In addition, pursuing higher education while shouldering domestic duties is getting harder.

Student parents struggle to find day care, a resource that has been slowly vanishing from U.S. college campuses: Fifty-three percent of two-year schools and 55 percent of four-year schools offered the service in 2003, compared with 46 percent and 51 percent, respectively, in 2013, according to the IWPR.

They have trouble paying for day care, an expense that rivals the cost of tuition. In California, for example, the average annual cost of care for an infant is $12,068. Annual tuition in the University of California system, not including room and board, is $12,804.

And student parents rack up more debt on average than the general college population, sometime using student loans to cover the day-care bill, advocates say.

A year after graduating, student parents who take out loans owe an average of $28,350 — about $3,000 more than their peers without kids.