A Chicago school's controversial policy of banning pupils from bringing lunches from home is aimed at encouraging healthy eating, the principal said.

Elsa Carmona of the kindergarten-through-eighth-grade Little Village Academy said pupils must eat the lunch served in the cafeteria unless they have a medical reason to bring their own food, the Chicago Tribune reported Monday.

"Nutrition-wise, it is better for the children to eat at the school," Carmona said. "It's about the nutrition and the excellent quality food that they are able to serve [in the lunchroom]. It's milk versus a Coke. But with allergies and any medical issue, of course, we would make an exception."

A spokeswoman for Chicago Public Schools said there is no "formal policy" about the issue and the decision of banning homemade lunches is left up to the principals.

Some parents have complained about the policy.

"Some of the kids don't like the food they give at our school for lunch or breakfast," parent Erica Martinez said. "So it would be a good idea if they could bring their lunch so they could at least eat something."