Juvenile obesity may begin at home, but thousands of U.S. schools have signed contracts that feed the growing problem.

Over half of all high schools and junior high schools nationwide have struck deals with soft-drink companies or vendors, giving them exclusive marketing rights to their students, according to the Institute of Medicine, a health policy adviser to Congress. In exchange, the schools often get five- or six-figure payments that cover benefits their budgets don’t, such as SAT test fees for low-income students, new scoreboards, uniforms and even proms.

The problem is that the marketing deals often promote consumption of foods that are a nutritionist’s nightmare. Pennsylvania school food-service directors, for example, reported in June that their cafeterias’ best sellers were, in rank order: pizza, hamburgers and sandwiches; cookies, crackers, cakes and pastries; french fries; potato chips and cheese puffs; and sodas and sugary sports drinks.

Since, according to the institute’s study, 40 percent of kids’ daily food intake occurs while they’re at school, schools are implicated in a worrisome trend: Childhood obesity has doubled among teens and tripled for kids ages 6 to 11 since the 1970s. That’s according to the Institute of Medicine’s study, “Preventing Childhood Obesity,” which was released Sept. 30.

That’s no surprise to Diana Frey, a junior at Montgomery-Blair High School in Silver Spring, Md. “A lot of kids don’t even have time for breakfast, then they eat a crappy lunch here,” she said. “That’s a good eight hours without eating anything healthy at all.”

School meals served as part of the National Lunch and Breakfast programs aren’t the problem. Schools must provide specified amounts of vitamins and nutrients to be reimbursed by the Department of Agriculture under these programs. Rather, it’s food sold in vending machines and lunchtime a la carte lines that often has no nutritional standard and is intended to be popular – and profitable.

At Montgomery-Blair, a school that’s trying – largely in vain – to shift student tastes toward healthful fare, nutritional value isn’t what sells food, according to students.

“It’s really just what’s available and what tastes good,” said Elena Pinsky, a junior. “We get inundated with information about healthy eating, the food pyramid and whatever, but in the end you can choose whether or not to listen and most people don’t.”

Senior Nick Falgout agreed.

“Kids just don’t see how what they eat now will affect them in the immediate short term, so they don’t really pay attention,” he said. A case in point, Falgout noted, was his own lunch of Crunch and Munch, a sugary popcorn snack.

One ironic result is that low-income students who eat subsidized meals tend to eat better than their wealthier peers, according to Margo Wootan, the nutrition policy director at the Center for Science in the Public Interest, a nutrition-promoting group in Washington. On the other hand, students rich and poor often shun subsidized meals as a form of welfare.

Montgomery-Blair is in a bind, Principal Phillip Gainous said. It signed an exclusive marketing deal with Pepsi in 1997, which currently pays the school $55,000 a year. The contract comes up for renewal soon, however, and the Montgomery County school system recently issued guidelines aimed at improving nutrition. Out went the soft drinks in Montgomery-Blair’s vending machines. In came fruit juices, chocolate milk and water. Pepsi’s vending-machine revenue has plummeted, according to Gainous. Pepsi may not renew the deal.

“The money is absolutely vital to the operation of the school,” said Gainous, who’s used it to buy computers and subsidize fees for SAT, achievement and Advanced Placement tests for low-income students.

“How are my kids from poorer areas supposed to compete with affluent kids without this money? If I push them to take these tests to get into college,” he said, “I have to be prepared to pay for them.”

Other schools have switched with better results. North Community High School in Minneapolis, for example, found that it made $4,000 a year more selling water in its vending machines than it did selling soft drinks.

The biggest school nutrition experiment is under way in California, where coalitions of parents, students and pro-nutrition groups won a state-wide ban on soft drinks in elementary and middle schools, which went into effect in July. Nearly 40 percent of elementary schools nationwide have deals with soft-drink companies, according to the study.

“We know that children learn from what we tell them, but we need to remember they also learn from what we sell them,” said Harold Goldstein, executive director for the ban’s leading promoter, the California Center for Public Health Advocacy.

Soft-drink companies maintain that banning products isn’t an effective strategy for curbing obesity.

“We need to teach people how to make their own choices, and you don’t teach people things just by restricting them,” said Kathleen Dezio, a spokeswoman for the American Beverage Association in Washington. “We believe students need choice in order to be taught what a healthy lifestyle is.”

Students, parents and officials who’ve fought school nutrition wars say resistance arises on several fronts.

Among them are contracts with vendors tend to make school officials promoters of their products.

Since 2002, the Charleston County School District in South Carolina has been defending a five-year, $8.1 million contract with Pepsi over parents’ objections.

“The district just says they are giving the kids what they want and that soft drinks have been in schools for years,” said Doug Bostick, a parent of two students in Charleston schools. “There’s a whole host of excuses.”

Katie McClure, the contract administrator for Charleston’s schools, said the vending machines remain off during lunchtime and also sell juices and water.

Goldstein, of the California Center for Public Health Advocacy, is unimpressed.

“Soft drink-sponsored schools are basically selling the health of their students to balance their bottom line,” he said.

Another problem is that controlling school cafeterias doesn’t control what students eat.

“Right around the corner, there’s a 7-11 and a McDonalds,” said Montgomery-Blair’s Frey. “If a kid wants soda, they can just bring it in.”

Students are supposed to stay on campus during lunchtime, Gainous reported, but they don’t.

Moreover, schools become dependent on vending contracts to ease tight budgets.

Wootan, of the Center for Science in the Public Interest, suggested car washes and raffles to make up for some of the lost revenue, but the idea didn’t go over well with students.

“Students already feel like they spend too much of their time at school,” said Montgomery-Blair junior Chris Consolino. “They wouldn’t give up any more of their free time, and even if they did, it wouldn’t be enough.”

In the end, since dietary patterns are set at home, nutrition is really a parental responsibility.

“It’s the parent who should be talking to their kids about what and what not to eat,” Gainous said. “By high school, eating patterns are already set. It doesn’t make a difference to just not have junk food in schools.”

The study concluded that schools, parents, kids, vendors and advertisers all bear responsibility for childhood obesity.

“There is no single group that owns this problem and no single group has the solution,” said George Flores, a contributor to the institute’s report. “We all need to work to create the most nutritious environment possible in our schools.”