Marietta, Ga. ? As Garin Hughes picks through his school-lunch burrito and unidentifiable apple-pear dessert, he has a secret.

Hidden underneath the eighth-grader’s right leg is a chocolate cookie in shrink-wrapped plastic. That’s for dessert.

In the past, his parents had no clue when he bought a treat at school. Now, thanks to a new school-lunch monitoring system, they can check over the Internet and learn about that secret cookie.

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

“My parents do care about what I eat. They try, like, to keep up with it,” said Hughes, a 14-year-old student at Marietta Middle School.

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

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 then is deducted from the student’s account.

The system was initially designed as a convenient way to make sure children bought lunch without worrying that lunch money would get lost, spent on other things or stolen.

Marietta Middle School eighth-grader Merwing Olivares enters his code into a MealPay keypad in the line at the cafeteria of the school in Marietta, Ga. Students enter their codes into a MealPay keypad when they purchase their food and then their parents are able to see what they bought for lunch via a computer terminal and the Internet.

However, these days parents increasingly are interested in what their kids eat away from home. It was requests from concerned parents that prompted Horizon Software to develop the online meal-monitoring option.

Under the system, parents can see all of a student’s lunch purchases. Even those paid in nickels and dimes – instead of the prepaid lunch account – are recorded in the system, said Tina Bennett, program director.

“A parent could give a child $20 and within two days that money’s gone. This allows them to see if they bought chips,” Bennett said. “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 at a Hoschton middle school was buying and found she was getting an extra 12-ounce can of juice each day, even when a four-ounce bottle of juice came with lunch.

“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 Dr. David Ludwig, director of the obesity program at Children’s Hospital Boston.

The biggest challenge for many school lunch programs, though, is “moving things clearly not good for kids out and making the choices more appealing,” said Dr. Douglas Kamerow, an obesity expert at RTI International and a member of the Institute of Medicine panel that released a report on childhood obesity last fall.

“The problem in general is the a la carte system,” said Kamerow, also a professor of clinical family medicine at Georgetown University. “Now you can buy french fries, chips and a Coke, and it’s called lunch.”