As Garin Hughes picks through his school lunch of a burrito and an apple-pear dessert, he has a secret.

Hidden beneath the eighth-grader's right leg is a chocolate cookie in shrink-wrapped plastic. That's his real dessert.

In the past, his parents had no clue when he purchased a treat at school. Now they can easily find out, thanks to a new school-lunch monitoring system that allows parents to check over the Internet what their children are buying in the cafeteria each day.

Health officials hope it will increase parents' involvement in what their children eat at school. It is a concern because federal health data show that up to 30 percent of U.S. children are overweight or obese.

"My parents do care about what I eat. They try, like, to keep up with it," said Hughes, 14, a pupil at Marietta Middle School.

Three school districts in the Atlanta area last week became the first in the nation to offer the parental-monitoring option of an electronic lunch payment system called Mealpay.com, created by Loganville, Ga.,-based Horizon Software International.

For two years, the payment system, used by 1,000 school districts in 21 states, has allowed parents to electronically prepay for student lunches. Students type in their identification number before the cafeteria cashier rings up each day's lunch bill. The bill is then deducted from the student's account.

The system was initially designed to make sure children purchase lunch without worrying that lunch money would get lost or spent on other things, or even stolen by bullies.

But because of growing awareness of childhood obesity, parents increasingly are interested in what their kids eat outside the home. It was that interest, more specifically requests from concerned parents, that prompted Horizon Software International to create the online meal-monitoring option.

Under the system, parents can see all of a student's lunch purchases -- those paid with a prepaid lunch account as well as those paid in the nickels and dimes from a student's allowance.

"A parent could give a child $20 and within two days that money's gone. This allows them to see if they bought chips," said Tina Bennett, the program director. "What we're really hoping is to get parents' involvement, to let them know what's happening."

Mary Carol Eddleman looked into what her daughter was purchasing at school and found that she had been buying an extra 12-ounce can of juice each day, even when a four-ounce bottle of juice comes with lunches at Osborne Middle School in Hoschton, Ga.

"That's about 150 extra calories a day. It's one thing if she did it occasionally, but she was getting in the habit of buying it every single day on top of lunch because her friends are drinking it," Eddleman said. "They drink it down like a Coke."

Eddleman talked to her daughter, who has since switched to buying a bottle of water instead.

"Any system that would help parents understand what's happening to their children's diets while at school . . . undoubtedly will help by raising awareness to the problem," said David Ludwig, director of the obesity program at Children's Hospital Boston.

The biggest challenge for many school cafeterias is "moving things clearly not good for kids out and making the choices more appealing," said Douglas Kamerow, an obesity expert at RTI International.

Merwing Olivares enters his ID code into a keypad at his school cafeteria in Marietta, Ga., allowing his parents to see on the Internet what he bought.