The Associated Press reports that 9 out of 10 schools sell junk food, with candy, soda, pizza and other snacks competing with nutritious meals.

Already plentiful in high schools, junk food has become more available in middle schools over the past five years, according to the Government Accounting Office (GAO), the investigative arm of the U.S. Congress.

"Parents should know that our schools are now one of the largest sources of unhealthy food for their kids," said Senator Tom Harkin, who asked for the study.

The big problem: Obesity among children and teenagers more than doubled in the past three decades, says the government-chartered Institute of Medicine. Obese kids will become adults with chronic health problems, said Harkin. Which in turn, means the U.S. health care system will be strapped.

He and other lawmakers want the government to set nutrition standards for food throughout schools and not just in the cafeteria.

Giving kids healthier options "should not be a suggestion, it should be a requirement," said Senator Patrick Leahy (Democrat, Vermont). Studies show that kids are suffering from higher rates of diabetes, high blood pressure and other illnesses normally associated with adults.

At issue (#1): Snacks such as candy, soda, pizza and popcorn are available in a la carte lines in cafeterias, in vending machines and in school stores. The GAO says the junk food crowds out healthier food such as apples, milk and yogurt in vending machines and school stores.

At issue (#2): Schools raise substantial dollars from selling snack foods: An estimated 30 percent of high schools raise more than $125,000 annually.