Despite lore from parents and grandparents about the caddying jobs or serving gigs they used to pay for school, today’s young adults know the idea of working your way through college is about as antiquated as milk delivered daily in glass bottles or Mad Men-era martini lunches.

Now there is more evidence to back that up. There is no state in the country where low-income students can afford to attend a public four-year or community college by combining the earnings of 10 hours a week of minimum wage work and grants, according to a study published Tuesday by Demos, a left-leaning think tank.

The analysis is rooted in a concept called the Rule of 10, which defines a college as affordable if families can cover the net price — or the listed price minus aid — through 10% of their income for 10 years, plus 10 hours of minimum wage work by the student. But that’s for families who aren’t considered low-income. As part of the formula, developed by a consortium of higher education experts convened by the Lumina Foundation, a non profit that works to increase the share of Americans with post secondary degrees, families earning $30,000 a year or less aren’t expected to contribute a portion of their income to the cost of college because theoretically their wages would be devoted to basic needs.

The assumption that students should work their way through school underpins the way some policy makers view our higher education system, said Mark Huelsman, a senior policy analyst at Demos and the author of the paper. But that assumption is no longer realistic, he said.

“You have students working longer and taking on debt in order to complete a degree that’s more important than ever” in the labor market, he said.

The paper offers some strategies policy makers could use to make it easier for students to work their way through school, including increasing the maximum Pell Grant — the money low-income students receive from the government to attend college — raising the minimum wage and upping state funding for higher education. In Hawaii and North Carolina, the gap between what low-income students earn doing 10 hours a week of minimum wage work and the average net price of college in the state is about $10,000 a year. In New Hampshire the gap is nearly $40,000.

That wide range is largely the result of different approaches to higher education funding, according to the study. North Carolina and Hawaii fund higher education at levels above the national average, whereas New Hampshire has cut funding for public colleges and universities by at least 30% since the Great Recession, the study notes.

“There is a certain subset of our political class that is fairly out of touch with the costs facing students,” Huelsman said.