It’s hard to picture a school lunch tray without chicken nuggets. But starting next summer, the breaded, bite-size childhood staple may be wiped from cafeteria menus across New York City public schools.

New food standards announced this week for nearly a dozen city agencies, including the Department of Education, will ban processed meats, create new restrictions on artificial colors and preservatives, further limit low-calorie sweeteners and aim to increase offerings of “minimally processed plant protein foods.” The standards, which go into effect in July 2026, apply to public schools and hospitals, and to agencies that serve older adults and homeless people, among others.

“When we came into office, we committed to ensuring all New Yorkers have access to healthy, fresh foods,” said Mayor Eric Adams, who has said his own health had improved after a shift to a plant-based diet. “By looking at the meals we serve, we are making New Yorkers healthier and achieving our mission of making New York City the best place to raise a family.”

What constitutes healthy eating has become increasingly politicized, from the push by Michelle Obama, the former first lady, to make school lunches healthier to the Make America Healthy Again movement spearheaded by the health secretary, Robert F. Kennedy Jr. The Trump administration, in a departure from its predecessors, is now letting some states bar residents from using food stamps to buy soda and other items considered unhealthy.

The changes in New York City, issued by the Mayor’s Office of Food Policy, aren’t the first time Mr. Adams has tried to put his mark on school lunches. In 2022, after he introduced “Vegan Fridays,” parents shared photos of their children’s lunches on social media, including prepackaged burritos, bags of Tostitos chips and apple slices. Lacking the appeal and alliteration of “Taco Tuesday,” the vegan day didn’t catch on.

Now educators and scholars say they are concerned about how the new food standards could negatively affect children’s eating habits, even if they are well-intentioned.