Whole-grain crackers, low-fat yogurt, fruit and water could become the school snacks of the future, driving out fattening fancies such as cola and fried chips.

The Institute of Medicine on Wednesday recommended new standards for school snacks and foods that sharply would limit calories, fat and sugar while encouraging more nutritious eating.

Concerned about the rise of obesity in young people, Congress asked the institute to develop the standards. Law now will consider them, as will state and local school officials.

"Making sure that all foods and drinks available in schools meet nutrition standards is one more way schools can help children establish lifelong healthy eating habits," said Virginia A. Stallings, head of the committee that prepared the report.

"Foods and beverages should not be used to reward or to discipline for academic activities or behavior," said Stallings, director of the nutrition center at Children's Hospital of Philadelphia.

Food sold in school cafeterias under federally assisted lunch programs already must meet nutritional standards. The institute's recommendations cover items considered competitive with those foods. Examples include snacks in vending machines and other food and drinks sold at school but not under the federal program.

Selling these foods is a money maker in some communities. Janey Thornton, president of the School Nutrition Association, said she expects complaints about losing this source of money if the recommendations are adopted.

"Shame on us if we try to balance the school budget based on the nutritional health of kids," Thornton said, whose organization represents school food service directors.

The standards would not apply to bag lunches that students bring from home.

Sen. Tom Harkin, chairman of the Senate Agriculture, Nutrition and Forestry Committee, said the recommendations "offer a tool kit for local, state, and federal policymakers who already know that we need to do more much more - to promote sound child nutrition and prevent childhood obesity."

Thornton said she thinks the report does not go far enough because there is no system for enforcement.

"We would like to see national standards for (school) food and beverages" that the Agriculture Department could enforce, she said.

The standards would help children learn the principles of good nutrition which they could also apply at home, said Thornton, child nutrition director for the Hardin County School District in Kentucky.

But the Center for Consumer Freedom worried that the report could lead to a government "no child with a fat behind" program.

The growing rate of obesity is caused by lack of physical activity rather than overeating, according to the group, which describes itself as representing restaurants, food companies and individuals.

The American Beverage Association, which represents companies that make and sell nonalcoholic beverages, said it is working with schools to "improve the product mix" sold in schools.

The report lists a first tier of foods that would be allowed at all grade levels during the school day and during after-school activities.

These foods would have to provide at least one serving of fruits, vegetables, whole grains or nonfat or low-fat dairy. There would be limits for fat, sugar and salt.

Examples are whole fruit, raisins, carrot sticks, whole-grain low-sugar cereals, some multigrain tortilla chips, some granola bars and nonfat yogurt with no more than 30 grams of added sugars. Drinks would be limited to plain water, skim or 1 percent milk, soy beverages and 100 percent fruit or vegetable juice.

A second tier of foods would be available only to high school students and only after school hours.

These foods would be limited in calories, salt, sugar and fat; drinks could have just have five or fewer calories per portion and no caffeine.

Examples include single servings of baked potato chips, low-sodium whole wheat crackers, graham crackers, pretzels, caffeine-free diet soda and seltzer water.

At the discretion of coaches, sports drinks would be available to students involved in an hour or more of vigorous athletic activity.

The institute is a branch of the National Academy of Sciences, an independent organization chartered by Congress to advise the government on scientific matters.