But then again, they may not.
The new deal was lauded by some as a good effort and criticized by others as toothless.
Five big makers of snack foods who agreed to the plan said Friday that they would discourage schools from stocking vending machines with treats that are high in calories, fat, sugar and salt.
The companies, Kraft Foods Inc., Mars Inc., Campbell Soup Co., Dannon and PepsiCo Inc., agreed to instead begin promoting snacks that meet new nutrition guidelines backed by the American Heart Association.
"This is voluntary, they don't have to do it," Clinton acknowledged, speaking of the companies and the schools. "But they recognize the challenge we face and they are helping us take the first step."
For some of the companies — which make everything from M&M's, yogurt and granola bars to Frito-Lay potato chips — that will mean reformulating some products or introducing new lines of healthier snacks for kids.
For others, it will mean urging schools to buy healthy, rather than cater to student cravings.
Fatty, calorie-ladden candy bars, extra-salty soups and anything with trans-fatty acids will be out. Low-fat chips (baked, not fried) and low-sugar yogurts will be in.
Announcing the initiative in a high school gymnasium in Harlem, Clinton agreed the plan's success will depend heavily on the participation of schools, which will continue to be free to buy whatever they like.
But he said the nation's childhood obesity epidemic and skyrocketing health care costs made immediate action essential.
The initiative got mixed reviews from those worried about what kids eat.
Janey Thornton, president of the School Nutrition Association and a child nutrition director in Kentucky, called the program commendable, but said it shouldn't be seen as a substitute for federal legislation enacting stronger health standards for school food.
"It has to have some enforcement behind it," she said. "We have some pretty strict regulations here in Kentucky, but some states have none, and that's where I think the problem comes in."
The Center for Science in the Public Interest, a consumer group, said the agreement would lack punch if schools and vending machine companies decide to keep buying chips and candy.
The food guidelines set under the agreement were more widely praised.
Under the rules, snacks marketed to schools wouldn't get more than 35 percent of their calories from fat and more than 10 percent from saturated fat. There will be a limit of 35 percent for sugar content by weight.
Those rules would mean students in participating schools would have to say goodbye to the regular-sized Snickers bar, which gets 130 of its 280 calories from fat, and contains 30 grams of sugar, out of 58.7 total.
In May, the alliance announced an agreement with beverage industry leaders to sell only water, unsweetened juice and low-fat and nonfat milk in elementary and middle schools.
The problem the group is attacking is one that was born in the mid-1980s, when money-strapped schools across the country began opening their doors to private vendors, and offering a wider variety of foods — letting many millions of students sate their hunger and thirst with chips and soda, rather than what was on the school lunch menu.
Winning those kids back over to healthy food might be a tough task.
Children pouring out of a Harlem elementary school a few blocks from where Clinton spoke Friday carried bags of chips, sodas and containers of greasy cheese fries, along with their books.
"Junk food is great," said 13-year-old Victor Jimenez.
Carlos Rodriguez, 13, said his school already stocks its vending machines with health food — but it hardly matters.
"Kids will buy what they want," he said. "We just stop by the bodega on the way home."