Kids in search of a healthy snack at school may be out of luck, and instead have to revert to an unhealthy one instead, says a new report by the Kids’ Safe and Healthful Foods Project, a joint initiative of The Pew Charitable Trusts and the Robert Wood Johnson Foundation.

“Research shows that the consumption of 110 to 165 calories above recommended amounts per day—roughly the difference between an apple and a bag of chips—may be responsible for rising rates of childhood obesity,” says Jessica Donze Black, director of the Kids’ Safe and Healthful Foods Project. “Because many students consume as many as half of their daily calories at school, what children eat during the school day is a critical issue if we want to reverse obesity rates.”

Childhood obesity rates have more than tripled in the past 30 years. The associated costs have been steadily rising, too. A University of Maine study says the medical costs of obesity for children and adolescents in the state could reach $1.2 billion over the next 20 years.