When thousands of Fairfax County public school students head back to class next month, Little Debbie won't be there to greet them.

The snack cakes have been banished from high school vending machines, along with Lorna Doone cookies and popcorn. Traditional Oreo cookies are gone, too, but Oreo Thins -- at 100 calories a pack -- remain. And when students file through the lunch line Sept. 13, they'll find their hamburgers tucked in whole-wheat buns.

The Fairfax County school system, which provides meals to about 140,000 people each day -- including students, staff members, senior citizens and some private-school children -- has long had a reputation for offering nutritious options. (Some days, students and other customers can munch on baby carrots and sticks of jicama served with a low-fat dip.)

But with concern mounting that the nation's children are piling on too many pounds, Penny McConnell, director of the school system's food and nutrition services department, never stops searching for the most healthful alternatives.

"I look at it like we're all partners in this whole childhood obesity issue," McConnell said. "In recent years, there's more emphasis on making sure we all make healthy choices. We feel we need to be as diligent as we can be."

So this year, raw zucchini will be added to the menu. The system also has switched to a whole-grain pasta that will be unveiled in October. And there's a new rule for middle school students: They can buy french fries only as part of a balanced lunch.

"Last year, some of them were purchasing two french fries, and that was their lunch," McConnell said. "We're saying no."

No new items are served in school cafeteria lines without being tested by the toughest critics -- the students -- at monthly tasting parties. The whole-grain pasta and hamburger buns earned mixed reviews last spring, but McConnell opted to make the switch because the federal government's new food pyramid encourages Americans to consume more whole grains.

Fairfax also has embraced Gov. Mark R. Warner's Nutrition and Physical Activity Scorecard and Awards Program, which recommends nutrition and fitness goals for schools. That program encourages schools to offer only foods that meet strict nutritional guidelines. (For example, it suggests that any snack sold on campus, with the exception of nuts, provide no more than 30 percent of calories from fat.)

That means that some chips, cookies and pastries no longer will be stocked in school vending machines. But students who need a little energy to boost their brainpower can reach for packs of Wheat Thins, pretzels, a low-fat brownie and even baked Doritos. And although several ice cream choices were eliminated, the system found an ice cream sandwich and a banana cream ice cream treat that meet the standards.

McConnell, who visits classrooms to talk to students about healthful eating habits and reading nutrition labels, teaches that moderation is the key to good health. The occasional treat, she says, is a good thing.

To that end, one item that doesn't meet the governor's standards -- fresh-baked chocolate chip cookies -- won't be removed from the menu.

"I'm a believer that there's no good or bad food," McConnell said. "It's about portion size and variety. There's nothing wrong with eating a chocolate chip cookie."