The old adage "You are what you eat" has special meaning for parents of school-aged children. Numerous studies have shown that children who don't eat well tend to not do well in school.

"You can usually tell which kids don't eat breakfast," says Kathy Davies, an early literacy specialist and former Grade 3 teacher at Magrath Elementary School. "Children who skip breakfast have trouble concentrating in class, especially in the morning."

Davies's observations echo the results of numerous scientific studies on the relationship between nutrition and cognitive performance. The studies showed that memory function correlates directly with levels of blood glucose. Students who hadn't eaten a good breakfast before coming to school had difficulty recalling words and facts, as well as doing arithmetic. Other studies have shown significant links between poor eating habits and attention deficit disorder (ADD), hyperactivity, depression, moodiness and chronic fatigue.

"I had one student who was really lethargic in the mornings and couldn't pay attention in class," says Davies. "He was coming to school without breakfast on a regular basis. But it's not just that kids don't eat meals—it's what they eat as well."

She recalls one student who was grossly overweight and lacked energy. "I know all he ate for lunch was chips and pop. I tried to teach him about the benefits of eating fruit and other good foods, but he was so used to eating junk food that he wouldn't even try anything else. When his grandmother packed him a sandwich he would throw it out. It was really too bad, because the other kids used to make fun of him and exclude him from their games."

Studies also show that highly caloric meals have a negative impact on a child's ability to concentrate—children who eat high-fat, high-sugar meals are sluggish afterward and don't pay attention to their lessons.

According to Heather Komar, a nutritionist who works with schools, kids will eat good food if that's what's available when they're hungry. "A survey they did in the U.S. showed that 32 percent of school-aged children drink pop, instead of milk or juice, with their lunch. But kids will switch to milk, chocolate milk or pure juices when they're the only things available in school vending machines or cafeterias."

Substituting healthy foods that students will eat for foods with high fat content or just empty calories is one strategy recommended by both teachers and nutritionists. Children who hate vegetables, for example, will often eat fruit. Children who won't touch plain milk may enjoy chocolate milk, cheese or yogurt.

Parents whose children are fussy eaters should also remember that small children have small stomachs. Instead of giving them a sandwich, muffin and fruit in their packed lunch, parents might save the fruit and cookies for an after-school snack. "It really bothers me to see how many of my students throw away the apple or banana their mom puts in their lunch boxes," Davies says.

She also recommends that parents introduce new foods gradually and one at a time. For example, many youngsters who won't even look at cooked vegetables at the dinner table will relish raw carrots, garden peas or celery sticks. "Whenever we had school parties, I would ask for platters of veggies and fruit and dip, instead of just sweets and high-fat foods," Davies says. "I remember one little boy who looked at this beautiful plate of food and starting making faces. But when he tried some broccoli and dip, he quite liked it."