Chuck Gross grabbed a Ziploc bag filled with his seven children’s birth certificates and climbed into the family’s blue Lexus.

He took a left, three rights and, two minutes later, pulled into the closest school campus, one of 19 meal distribution sites that Prince William County Public Schools has set up to feed its 92,000 students — 44 percent of whom rely on federally subsidized meal programs — during the novel coronavirus-driven closure of all Virginia public schools. Gross, an out-of-work IT specialist, looked at the bagged breakfasts and lunches on Tuesday morning. They were, he knew, his family’s only hope for food that day.

He also knew he might be violating school policy (shaped, he would later learn, by federal guidelines). Other parents had told him that to receive meals, his children should have come in the car with him.

“He told [school staffers] we weren’t able to do that,” his wife, Jeni Gross, recalled, explaining that three of the couple’s children have compromised immune systems, making them more susceptible to the virus that causes covid-19. “He said that we weren’t willing to put them at risk.”

Staff members refused, twice, to give him food. So Chuck Gross pulled out the birth certificates — “and they still turned him away,” Jeni Gross said.

As school closures continue to mount and a rapidly implemented halting of American life sparks unemployment, public school meals are becoming essential to an escalating number of parents throughout the nation. But a federal policy requiring that students come in-person to pick up free meals is forcing families with immunocompromised children into a wrenching calculus.

“Do I go get the food and risk my child’s life?” asked one mother in Prince William County whose 7-year-old is immunocompromised. “Or do we go hungry, but stay safe?”

During a conference call between Virginia public schools and federal officials last week, Prince William employees asked the U.S. Agriculture Department — which oversees school meal programs — to reconsider its policy of in-person pickups. The school system has not heard back, said Adam Russo, director of Prince William’s office of school food and nutrition services.

“Our staff is not able to serve a meal without a child present, and that has not changed even with the pandemic,” Russo said. “This is a hardship on our program and our families.”

The USDA did not respond directly to a question asking whether it would alter its food distribution policies to accommodate families with immunocompromised children. Agriculture Deputy Undersecretary Brandon Lipps said in a statement that officials are working to review the agency’s “new legal flexibilities” provided by Congress during the coronavirus crisis to “ensure we can remove any roadblocks to feeding low-income children during this difficult time.”

In a separate statement, Agriculture Secretary Sonny Perdue pledged to collaborate with school system leaders.

“Local school nutrition professionals know how best to feed their children, and we are working with them and their partners to give greater flexibilities and waive restrictions,” Perdue said.

It is difficult to calculate how many families nationwide have children with compromised immune systems, although the number probably reaches well above tens of thousands, said Amanda Stewart, a pediatrician at Boston Children’s Hospital. Immune system deficiencies — which render the body less able to detect infection and to repel it — happen for myriad reasons, including genetic diseases, HIV and blood disorders.

An especially common cause in children is leukemia, Stewart said, because cancer treatments such as chemotherapy effectively wipe out immune systems. In 2016, about 57,000 American children were living with cancer, according to the Centers for Disease Control and Prevention.

For families who fall into this category, Stewart said, it is vital to keep children at home as the coronavirus spreads. Health experts suspect that — as is the case for other virus-related respiratory illnesses — it would take an “especially severe path” in immunocompromised individuals of all ages, the pediatrician said.

Stewart said families should allow immunocompromised children outside only for essential trips, such as visits to the hospital. It is especially important to keep these children away from crowded sites visited by other school-age students, she said — sites such as meal distribution centers.

“We know this virus can be aerosolized and stay in the air for some time, so it matters not only who’s there when you arrive but who’s been there recently,” Stewart said. “And with a lot of children in one place, children are higher-risk generally because they can transmit the virus without showing symptoms.”

It is unclear how many school systems are requiring students to show up in-person to receive meals. Some districts are asking only that families present student ID numbers at pickup sites, while others are delivering food to students’ homes on buses.

But for many school systems — especially those in rural areas with far-flung constituents — bus deliveries are impractical. In Prince William, Russo said, officials are unwilling to violate federal policy, partly out of concern that a misstep could lead to the program being shut down.

“Our priority,” he said, “is making sure that the food is available for the families that do arrive for the food.”

Virginia Del. Danica A. Roem (D) — who represents Manassas Park and parts of Prince William — said she hopes the USDA will issue the county a special waiver. But she said that action, alone, would be far from sufficient: She is calling for the federal government to issue a blanket order voiding the in-person requirement.

“As long as that USDA regulation is in place, it’s a barrier for access for people to get food,” Roem said. “The federal government needs to change that regulation, and they need to do it now. Covid-19 cases are rising every minute.”

The Gross family made a second attempt to gather food Thursday morning and were able to pick up meals for their children. It was a much-needed reprieve, said Jeni Gross, who has not allowed any of her children to leave the house for about two weeks.

The three children who are immunocompromised are of particular concern, she said: the asthmatic 8-year-old, a 14-year-old with small airways because of dwarfism and the couple’s youngest — a 6-year-old girl whom a chromosomal deletion has left blind, deaf and reliant on feeding and oxygen tubes.

Jeni Gross, who stays home to care for the 6-year-old, laments that the situation for families like hers remains uncertain.

“The policy has to change,” she said.

The mother in Prince William, whose children also attend the county’s public school system, has been less fortunate than the Grosses. She spoke on the condition of anonymity because her daughters, ages 16 and 7, fear they will be bullied for “being poor” if their names are published.

The 7-year-old was treated recently for cancer, resulting in an immune system deficiency. The coronavirus-driven restriction of daily public life has left the mother, a driver who works on contract, without employment. The Prince William meals are the family’s only source of food — and, the mother said, she needs every item in the four bagged breakfasts and lunches for which her two daughters qualify.

She has developed a rationing system: Her daughters each eat a cereal pack for breakfast, yogurt for lunch and a sandwich for dinner. The mother subsists on coffee and snack-sized packs of dried cranberries included with the meals.

The mother has explained to her youngest — whom she is not otherwise allowing to leave the house — why she must get in the car each morning. She has also, again and again, listed the precautions the family is taking: Each morning, the mother disinfects their entire home before her daughters wake.

When the family drives to pick up food, the 7-year-old sits in the far back of the car. When they arrive home, everyone removes clothes and showers immediately — and the mother sprays the 7-year-old with disinfectant.

None of this calms the girl, who is living in a state of near-constant terror. Things were especially difficult Wednesday morning.

“She said, ‘Oh, Mommy, I don’t want to go outside, I don’t want to get the corona, I don’t want to die,’ ” the mother said, beginning to cry. “I told her we have no choice: We need the meal.”

She couldn’t force the girls to cooperate on Thursday. But on Friday, she woke early, and prepared to do it all again.