First lady Michelle Obama vowed again Wednesday to fight attempts to delay enforcement of school lunch nutrition standards, expressing surprise and regret at proposals in Congress that would allow some school districts to seek waivers from requirements that they offer more healthful fare.

"I find myself surprised that we're here," Obama told a handful of health and medical reporters in her office, "because just a few years ago, everybody was around the table celebrating this victory, that school nutrition standards had been improved for the first time in 30 years. And everyone was on board."

"Of course it's hard" to wean students off pizza, French fries and other high-fat, high-sodium foods that had been staples of school lunches before passage of the Healthy, Hunger-Free Kids Act in 2010, she added. "We expected those challenges, particularly among our oldest kids, who've grown up eating junk food. But what we did not expect was for the grown-ups to...go along with them and say 'well this is too hard, it costs too much money. So let's just stop'."

Last month, the House Appropriations Committee voted to allow school districts to temporarily opt out of school dietary requirements.  Some school districts have complained that requiring whole wheat products and fruits and vegetables, in the name of reducing obesity among children and teens, has prompted older students to shun school lunches and breakfasts and is costing the districts money. The bill would allow the U.S. Department of Agriculture to give waivers to any school district whose lunch programs saw a net loss over six months.

The idea is supported by Republicans and the biggest lobbying group in the fight, the School Nutrition Association, which is allied with food companies that provide fare to the multibillion-dollar school meal market. It is sharply opposed by the first lady -- who has worked for better nutrition and improved fitness -- Democrats and health groups. Obama stepped up her work against the waivers at a rare news conference last month.

The Agriculture Department contends that more than 90 percent of schools are putting the reforms into effect, kids are eating more fruits and vegetables as a result and, despite evidence that some kids are dumping the new healthful fare, school lunch revenue increased during the program's first year.

Where there have been problems with certain food, such as whole-wheat pasta that proved inedible, the department has granted some schools more time to develop healthful menus, said Sam Kass, Obama's senior adviser for nutrition, who also attended the meeting.

Kass, Obama and James M. Perrin, president of the American Academy of Pediatrics, noted the association between reducing hunger and improving test scores, and Kass noted that obesity remains the most frequent reason why volunteers fail to qualify for military service.

Obama said that the administration is looking for ways to reinstitute cooking classes in school because children now eat out so often that they grow up not knowing how to cook. Americans now spend nearly half their food dollars eating outside the home, according to the National Restaurant Association, but home-cooked meals tend to be more nutritious, Kass said.

Persuading children to eat vegetables and other healthful fare takes effort, Obama said. "I find with my kids that you have to learn what works, and you've got to figure it out and you've got to involve them and you've got to listen to what they want to hear. But it's doable. But it's hard work."

"As a parent -- not as first lady, as a parent -- I'm not going to sit and watch my kids eating right knowing that there are millions of kids that somebody gave up on because it was just too hard. That's just not right."