Around 11:40 on a cool spring day in early April, students began to stream into the lunchroom at Haleyville High School in Alabama.

Cheerleaders, soccer and baseball players, and other members of the student body filed through the lunch line and sat at their tables. They chatted and laughed about upcoming games (go, Roaring Lions!) and prom as they dug into plates of chicken Alfredo, green beans and salad.

Emma Anne Hallman, standing in a corner, watched the teenagers carefully. As the child nutrition director for the Haleyville City School District, she has the job of feeding 1,600 students, in prekindergarten through 12th grade.

For months, Ms. Hallman and other heads of school lunch programs have worried about new federal regulations that would reduce allowable sodium levels and introduce new sugar restrictions for foods served in school cafeterias. A debate has raged, with many parents and nutritionists applauding efforts to make lunches more nutritious while some school lunch administrators fretted that the results will be less tasty to students, reducing consumption and increasing waste.

“We are cringing, as it could result in changes across our menus,” Ms. Hallman said. “We would have to look at the sodium amounts in the recipes of some of our students’ favorite foods, like chicken wings, hot wings or even some of the Asian foods.”

The job of feeding the nation’s schoolchildren has never been easy, but in recent years it has become particularly difficult. Rapid inflation has made it harder for schools to prepare meals at or below the cost of $4.30 per student, the federal reimbursement level for the roughly 30 million students who receive federally subsidized meals. Meanwhile, competition for labor has resulted in higher wages — putting a strain on lunch program budgets — and shortages of employees in some cafeterias.

“I can’t compete with what Amazon is paying,” said Betti Wiggins, the head of nutrition services for the Houston Independent School District, one of the nation’s largest school districts, which serves over 200,000 meals a day across 276 locations. Likening her program to a quick-service restaurant with annual revenue of $132 million, Ms. Wiggins said about 35 percent of her budget went to labor costs and half to food.

“I’ve got to pay for all of that with a budget of $4.30 per student, and I have some food manufacturers backing out, saying they can’t make the food at that cost anymore,” she said.

While far from perfect (cafeterias serve plenty of processed foods), school lunches are arguably much healthier than they were a few years ago, thanks to a signature program geared toward combating childhood obesity and championed by Michelle Obama when she was first lady. The Healthy, Hunger-Free Kids Act, passed in 2010, required schools to reduce the calories, fat and sodium in foods served in cafeterias and to increase offerings of whole grains, fruits, vegetables and nonfat milk.

The new regulations drew sharp criticism, however, and the Trump administration rolled back some of them, such as a prohibition on 1 percent chocolate milk. But last year, the Biden administration proposed updates that would gradually limit salt and sugar in school lunch foods in an attempt to meet federal dietary standards.

On Wednesday, the Agriculture Department made the new rules final after scaling back several provisions in the earlier proposal and shifting the start dates. Instead of gradually cutting sodium in lunch foods by a third from current levels by the fall of 2029, school cafeterias will have to cut sodium levels 15 percent by the 2027-28 academic year. And for the first time, schools will need to limit the amount of added sugars in cereals and yogurts, starting in the 2025-26 academic year.

Standing in a Haleyville School District pantry a few weeks ago, Ms. Hallman nodded to boxes containing cups of Cocoa Puffs and Cinnamon Toast Crunch cereal. They contain less sugar than the cereals that are bought from grocery stores and poured into bowls at home. Still, she said many of these foods would most likely be affected by the new rules and have to be reworked by the manufacturer. The label of a Cocoa Puffs cereal bar, for instance, showed it had eight grams of added sugar, while a frosted strawberry Pop-Tart had 14 grams.

“Breakfast, particularly grab-and-go options, is going to be tricky,” Ms. Hallman said. “The changes could affect how many times a week we can offer certain items with sugar to the students.”

Many nutritionists and health-policy watchdog groups say the new rules on sodium and sugar are important, with so many children struggling to have or make nutritious choices outside school.

The Center for Science in the Public Interest, an advocacy group, applauded the move to decrease the amount of sugar in foods served in schools, but called the smaller reduction in sodium levels a “missed opportunity, given that 9 out of ten kids consume too much sodium.”

“Nutrition standards, in general, are so contentious right now,” Meghan Maroney, the head of federal child nutrition programs for the group, said in an earlier interview. “But we have to do what the science says is best for kids’ health.

“I know schools and others are working on razor-thin margins, and it is a tough, thankless job sometimes, but schools and manufacturers need to figure out how to make this happen.”

Shortly after the Biden administration proposed the new limits on sodium and sugar early last year, Big Food began weighing in.

General Mills, which makes Cocoa Puffs and Cinnamon Toast Crunch, said in a public comment on the proposed rules that new sugar limits should be applied to a student’s weekly diet at school, rather than on individual items. It also requested that the potential start of the limits be delayed to allow manufacturers time to reformulate the products.

Another manufacturer, Ocean Spray, asked that sugars that are added to dried cranberries in the manufacturing of its products not be counted as part of any sugar limitation. The Dairy Farmers of America urged regulators to continue to allow flavored milk and to make whole milk an option at schools again. The group also argued that sodium from cheese should not be counted against overall sodium limits.

Executives at Tyson Foods, which provides chicken, pork and beef products to schools, said the new sodium limits, depending on where they were set, might limit the number of days per week that some popular products, such as chicken with a Buffalo sauce, could be offered.

And while Tyson works with suppliers and experiments with ingredients to come up with alternative spice blends that can the replicate the flavor of salt, sodium plays a critical role beyond making the food tasty.

“From a food safety perspective, sodium reduces the water in chicken and extends the shelf life by delaying spoilage,” said Alisha Deakins, an associate director of product development at Tyson.

Salt is also inexpensive compared with other spice options.

“We want to make sure the food is safe and cost effective for school districts,” Ms. Deakins said. “There are options out there that are alternatives to salt, but they come with potentially increased cost.”