And of course, the most controversial moment came when Ronald Reagan's budget director, David Stockman, proposed classifying ketchup as a vegetable to meet dietary requirements while also slashing costs.

Both federal and local officials have been trying to improve the school lunch programme, so it is more nutritious for students and the food is more liked by them. But it's a massive undertaking. The National School Lunch programme in the United States feeds more than 28 million students in 98,000 schools across the country.

Schools also provide breakfast in some districts to low-income children and, since 1998, the federal government has also given schools money to provide snacks to students who participate in after-school programmes.

In 2003, the US Department of Agriculture said the school lunch programme cost $7.1bn (£3.7bn). The menus vary greatly from district to district, but they must meet the applicable recommendations of the Dietary Guidelines for Americans. These say no more than 30% of an individual's calories should come from fat, and less than 10% from saturated fat.

School lunches are also required to provide one-third of the recommended dietary allowances of protein, Vitamin A, Vitamin C, iron, calcium, and calories.

The food is mostly packaged, with some critics complaining that lunchrooms are merely dumping grounds for agricultural surplus.

Dr Walter Willett, head of the department of nutrition at the Harvard School of Public Health, says of the foods offered to schools by the Department of Agriculture: "Their foods tend to be at the bottom of the barrel in terms of healthy nutrition."

A 2001 Department of Agriculture study showed that 80% of schools offered menu items that could be combined to meet dietary guidelines.

But more than one-fifth of lunch programmes offered commercial fast food, and most schools had vending machines. The study found that students often made bad choices.

But there are attempts at broader reforms.

A new programme partners schools with local small farmers to bring more fresh fruit and vegetables to students. And some states are pushing to ban vending machines in an attempt to keep the students from subsisting on snacks and junk food.