MINNEAPOLIS -- A study indicates that schools that have bake sales and schools where teachers reward students with candy are at risk of having more overweight pupils.

The lead author, from the University of Minnesota, said the research doesn't prove that those practices contribute to obesity, but she said there does seem to be a connection.

And that makes sense to Kevin Miller, a middle-school principal in Connecticut, which banned bake sales and junk food as part of a district-wide program. Miller said kids are actually eating apples and oranges instead of throwing them away.

And without any candy wrappers, he said, the hallways are spotless.

The University of Minnesota study looked at 3,000 eighth-graders in 16 middle schools. Researchers analyzed whether the schools had specific "food practices" that would give students access to food outside normal meal programs.

Thirty-one percent of schools allowed food in the classroom, and 38 percent allowed beverages in the classroom. Nineteen percent of schools allowed beverages in hallways, and 31 percent allowed snacks in the hallway.

Researchers found that the body-mass index of students was 10 percent higher for each additional food practice allowed in the school.

The study appears in the December issue of the Archives of Pediatrics and Adolescent Medicine.

"Food choice at school includes more than the foods and beverages offered as a part of school meal programs, a la carte, and in vending machines. Similarly, opportunities for eating during the school day extend well beyond the school lunchroom and breakfast and lunch," the researchers wrote.

The authors urge school nutrition policies that "consistently promote and support healthy dietary practices."

• Study Abstract