Kurt Marthaller, who oversees school food programs in Butte, Mont., faces many cafeteria-related challenges: children skipping the lunch line because they fear being judged, parents fuming about surprise bills they can’t afford, unpaid meal debts of $70,000 districtwide.

But at nearly half of Mr. Marthaller’s schools, these concerns have vanished. At those schools, all students get free breakfast and lunch, regardless of their family’s income. At one school, West Elementary, children grab milk cartons, cereal bars and bananas from folding tables on their way to class, with almost 80 percent of students eating breakfast there each school day.

“We’ve done a lot of good things to feed kids here in Butte,” Mr. Marthaller said. But introducing universal free meals, he added, was “probably the best thing we ever did.”

Advocates for free school meals have pushed for them to be offered to every student for a long time, but saw significant progress in the last decade and a half. Their first big win came quietly, in 2010, when Congress passed an under-the-radar policy called the community eligibility provision, which made it easier for schools to serve free meals to all. Then, during the Covid-19 pandemic, the federal government let every public school student eat for free, rapidly transforming the nation’s thinking around school meals.

Eight states have passed their own universal free meal legislation since the federal largesse ended in 2022. Dozens more have introduced similar bills or have one in the works. A surge of additional schools — nearly 7,000 — have signed up for the community eligibility program that West Elementary participates in: As of the 2022-23 school year, roughly four in 10 public schools were enrolled.

In total, more than 21 million American children now attend schools that offer free meals to all — a tenfold increase from 2010. “Schools did not want to go back to charging some kids,” said Crystal FitzSimons, the director of child nutrition programs and policy at the nonprofit Food Research and Action Center. “They saw the huge benefits of providing free meals to all students: supporting families, supporting kids, changing the culture of the cafeteria.”