Anyone who has ever tried to sneak healthy food into kids' lunches knows what Chicago Public Schools is going through.

Sometimes kids openly embrace the new food. Sometimes they eat it without realizing the difference. And sometimes they refuse it altogether.

CPS has met with all three reactions this school year, when it stopped serving daily nachos, Pop-Tarts and doughnuts and introduced healthier options at breakfast and lunch. But in a sign of how challenging this transition can be for schools, district figures show that lunch sales for September through December dropped by about 5 percentage points since the previous year, or more than 20,000 lunches a day.

During visits to several CPS schools over the last few months, the Tribune heard many accounts of students throwing away their lunches. Others say they opt for "cookies and slushies" from the canteen or wait to eat until they get home. And while some kids said they still like their school meals, the vast majority used the same word to describe the food: nasty.

"If they're going to feed us healthy, they need to feed us something good that's healthy," said Mijoy Roussell, a sixth-grader at Claremont Academy who was skipping lunch in favor of a packet of candy. "This food is disgusting, which is why I'm not eating lunch."

For the 2010-11 school year, CPS and its caterer, Chartwells-Thompson, switched to menus featuring more whole-grain products, less sodium and a wider variety of vegetables. Most cereals offered have less than 10 grams of sugar per serving.

Chartwells and CPS note that these changes exceed existing U.S. Department of Agriculture meal standards, but they appear to have created negative impressions of healthy foods among many students.

"They want us to eat healthy food, but the food has no flavor," sophomore Jacob Hernandez said as he picked at unsalted rice and beans at North-Grand High School. "Last year, they had a yellow Puerto Rican rice. But this year it's all dry, and you can tell they put a lot of stuff in there, but what's the point if there is no flavor?"

CPS' new lunch standards closely mirror new federal rules proposed by the USDA, offering a glimpse of the tests other districts soon may face. Many CPS students qualify for free lunches, but government funding for the meal program depends on their continued participation.

Louise Esaian, who oversees CPS' food service program, said introducing new concepts is always challenging, but officials want to help students start to realize they can make healthier choices at mealtimes.

"We are thrilled that 70 percent of CPS students choose to eat lunch at school," she said. "While there has been a slight decline in participation, it does not reflect the measurable and positive gains we have made as a school district in making improvements to the nutritional quality of our school breakfast and lunch programs."

School lunch experts emphasize that healthful options are a lot easier to sell when the food actually tastes good.

"Cooking flavorful food from scratch is not rocket science," said Kate Adamick, who specializes in revamping institutional food operations.

For example, CPS forbids the use of salt in the preparation of vegetables or other fresh food offered to students, although the district allows high levels of sodium in the processed foods it serves.

The results of this policy could be seen on recent visits to lunchrooms, where trays of boiled broccoli, zucchini and a pea-carrot mix sat virtually ignored by students. Many of those who did take the vegetables left them on the tray uneaten.

Chef Ann Cooper, who has worked to reform lunch programs in Berkeley, Calif., and Boulder, Colo., knows it's difficult to create healthful changes but believes it's a mistake to serve nutritious, scratch-cooked items entirely without salt.

"When you cook, you need the salt for food to taste good," Cooper said. "The majority of the salt in our diets doesn't come from using the salt shaker in cooking. It comes from processed foods."

To convert kids to healthier meals, she said, "first you have to get the (healthy) food to taste good, and then you have to look at other ways of reducing salt in other parts of the menu, like by taking out processed foods."

Yet last month, in response to sagging lunch sales, the district brought back a processed spicy chicken patty sandwich as a daily offering in all district high schools. The sandwich contains dozens of ingredients, the first three being chicken, water and "vegetable protein product."