Snickers for lunch? Now mom can eye student purchases.

Melissa Crowder grew up with a busy single father who worked for Frito-Lay. His idea of family dinner was often chips and dip.

Now, as a parent of three herself, Ms. Crowder is much more conscious of the kinds of foods her children eat.

"I had built up those habits as a child and I know how hard they are to break," she says. "I don't want that for my kids."

But she can't be everywhere all the time. That's why Crowder is so pleased with the newest offering from her school district north of Houston: MealPay, which allows parents to monitor electronically what their children are eating at school.

By prepaying their child's account, parents can log on and track their children's purchases, whether they be a banana or a bag of Doritos. The high-tech system even allows parents to ban certain foods at the register.

Now in 76 school districts in 24 states, MealPay comes at a time when physical activity for children is at an all-time low and obesity is at an all-time high. In the growing fight over proper nutrition, school districts are getting caught in the crossfire.

Some are taking matters into their own hands, while others are being forced into action by lawmakers.

This year, for instance, legislators introduced some 200 bills in 40 states. About a dozen became law, and they range from simply encouraging schools to set standards to outright bans on foods that list sugar as their primary ingredient, as happened in New Jersey and Connecticut.

And last year, Congress mandated that any school district participating in the federal school lunch and breakfast programs must develop and implement wellness policies on nutrition and physical education by the start of the 2006 school year.

That law was the impetus behind Atlanta's Cobb County School District getting MealPay throughout its 110 schools this year. MealPay works like an ATM: Parents or the school district must pay a transaction fee each time money is paid into an account.

"We also wanted a way to keep parents in the loop," says Cynthia Downs, executive director of the district's food and nutrition services.

She says the district has been getting positive feedback from parents who want to be more involved in their children's eating habits at school.

"As a country, I think we are making progress in addressing the issue of nutrition in schools - especially as people's understanding of the issue grows," says Margo Wootan, director of nutrition policy at the Center for Science in the Public Interest in Washington. "But childhood obesity is still of great concern."

With studies showing childhood obesity rates at 16.5 percent, she says monitoring services such as MealPay are good supplements but that they don't replace the need for improving school nutrition standards.

"All the choices should be healthy ones so children aren't tempted to make poor choices," says Ms. Wootan. "Nobody wants their kids to have a Snickers and a Coke for lunch, so why should that option be there in the first place?"

But schools are only one source of the problem, cautions Reginald Washington, cochairman of the American Academy of Pediatrics' Task Force on Obesity.

"A lot of people say if you remove vending machines from schools, you will take care of obesity. Other people say by increasing children's physical activity, you will take care of obesity. And still others say you need to close all fast-food restaurants to take care of the problem," he says. "But you are not going to have much of an impact by addressing only one of these issues."

Communities need to recognize the need for comprehensive programs, says Dr. Washington. He notes that the real potential behind monitoring services such as MealPay is to allow parents to encourage their children to make the right decisions when they are at school and help plan meals when they are home.

If children include fruit in their lunch, for example, parents can praise them for doing so. If they don't, parents can make sure they get extra fruit while at home.

Back in Shepherd, Texas, about an hour north of Houston, Crowder says she worries about her ninth-grade daughter, Hannah, who often does not eat lunch.

If she comes home cranky after cheerleading practice, her mother wonders and then checks her food record. A slushy and brownie for lunch reveal the problem.

While Crowder doesn't ban any of her children from buying certain items, she uses their slip-ups as opportunities to talk about proper nutrition.

"They are still growing and the habits they establish now they will carry through life," she says.