Hunger impedes learning.

Many UFT members have undoubtedly worked with the hungry child who has trouble concentrating or staying on task.

Over time, a child who is persistently undernourished can suffer serious developmental and learning delays.

In New York City, three out of four students in public schools qualify for free or reduced-price lunches. But nearly a third of those eligible — 250,000 students — don’t participate in the program. In addition, many families whose incomes are just above the $36,000 eligibility threshold are not able to take advantage of the meals served every day at their schools.

That is a wasted opportunity to get the children the nourishment they need.

One reason for the lackluster participation in the lunch program is the social stigma attached to it. This helps to explain why participation is highest in elementary schools, at 81 percent of those eligible, and drops to 61 percent in middle schools and 38 percent in high schools.

There is a way to boost participation and avoid the stigma: Offer free lunch to everyone.

Large school districts around the country, including Chicago and Boston, have adopted universal free lunch programs in recent years. Chicago, for example, reports that the change has increased participation by eliminating the need to collect applications from families or lunch money from students.

A coalition of 120 organizations and advocates in New York City is asking the city to consider a universal free lunch program here. Federal subsidies would cover most of the cost. The city would have to pay only $20 more per student per year, or about $20 million.

That is a small amount considering the huge benefits. With universal free lunch, an estimated 120,000 more children would take advantage of having a nutritious lunch every day.

That’s 120,000 more children who would have the nourishment they need to learn and to reach their true potential.