Montgomery County Public School buses in Bethesda, Md. (Photo by Katherine Frey/The Washington Post)

When school districts decide to stay open during inclement weather, many parents assume that it relates to the roads.

But there’s another reason schools are reluctant to grant snow days: Their students may have little to eat at home. According to the Agriculture Department, 20 million students receive free lunch, and 11.7 million receive free breakfast, at school.

Students are eligible for free lunch if their household income is 130 percent and below the federal poverty limit, and can receive a reduced-price meal if their household makes up to 185 percent of that limit. The USDA has found that participating children from food-insecure households get a significant amount of their daily calories and nutrients from the program.

“Many high-poverty schools consider the impact closing schools will have on their students access to school meals,” said Crystal Fitzsimons, the director of school and out-of-school-time programs at the Food Research and Action Center. “And it is an even bigger concern when the school closure is on a Monday, Friday, or goes on for multiple days.”

Representatives for the New York and D.C. city school districts cautioned that many factors go into the decision to call a snow day. Those include things such as the state of the roads, the status of local public transit, available learning time, and parents’ need to go to work during the day.

But food access is also a major concern, they acknowledged. And it has arguably become more important as schools have taken on more responsibility for feeding students. Between 2000 and 2016, the number of students receiving free or reduced-price lunch increased from 15.5 to 22.1 million. Those students also became a larger share of the total lunch-buying pool — from 57.1 percent in 2000 to 73.3 percent today.

As a result, many schools think long and hard about closing, particularly in areas where many students buy free- or reduced-price lunch. In fact, the role of schools is so important here that the government has urged them to serve meals even when school isn’t in session.

Last September, USDA sent a memo to child nutrition program directors, encouraging them to “be flexible” on snow days and similar days off and to provide breakfast and lunch, if it’s safe. Such measures guarantee, the agency’s Angela Kline wrote, that “students do not experience a lapse in food security.”

“Schools are very conscientious of the impact of both delays ... and closures on access to school meals,” added Diane Pratt-Heavner, the spokeswoman for the School Nutrition Association. “We have seen during teacher strikes that districts will open one or two schools specifically for meals. The same thing often happens following natural disasters.”

Of course, where food service is concerned, the easiest way to feed the most kids is still to feed them in school. And if you’re surprised by the lack of snow days this season, that may be a factor.

As Carmen Farina, the New York City schools chancellor, told local news after she declined to call a snow day during a major winter squall: “Many of our kids don't get a hot lunch and, in many cases breakfast, unless they go to school.”

More from Wonkblog:

Why grocery stores can’t seem to keep shelves stocked during snow storms

Milk and bread are actually pretty terrible survival foods

A record number of poor kids are eating breakfast — thanks to a program many conservatives hate