Please Sir, can I have some more?

From wholesome and nutritious food in the 1960s to the Turkey Twizzlers and fizzy drinks of today -

Queen's pudding. Manchester tart. Apple meringue pie. Pineapple sponge. Date pudding and custard. Banana jelly with cream. Milk pudding with rosehip syrup. Apricot flan. There was a sweet melodiousness to the puddings served to children in postwar British schools. They came fortified with fruit, milk and motherly love, to feed up growing bones. Doubtless, they were sometimes stodgy. Some children dreaded their semolina, and tried to hide it under their spoon when the teacher wasn't looking. But there is something about these names that produces a feeling of comfort - the feeling of being well provided for.

In the 1960s, all of these puddings were on the school menus for the Inner London Education Authority. An official pamphlet from 1967, Meals for School Children, shows just how much care went into the preparation of school meals in London. Green vegetables would arrive in a school kitchen three times a week to be sure of remaining fresh and crisp, with seasonal variation depending on "what is available". All vegetables should be cooked "for the shortest possible time", and without bicarbonate of soda. The pamphlet's author is enlightened enough to see that many children prefer raw vegetables to cooked and advises including watercress, tomato and parsley as well as grated raw cabbage. Potatoes were mashed, fried, roasted or boiled, but not generally chipped. Rosehip syrup was given for vitamin C, and because children liked its sour-sweet taste.

Perhaps the most impressive thing is the meat cookery. It wasn't all baked liver and spam fritters (though these did pop up on certain days). On the best days, the lucky children were treated to roast beef and Yorkshire pudding; cold veal and ham pie; stuffed lamb loin with mint sauce; steak and kidney pie; or beef olives. It was expected that every kitchen should have a stockpot, with bones procured from the butcher boiled down to make a good rich stock. Minced meat was not ready-minced, but bought in the piece and minced by the kitchen.

Compare this with the kitchen culture that greeted Jamie Oliver nearly four decades on when he arrived in the kitchen at Kidbrooke Secondary School in Greenwich for his recent Channel 4 series. Instead of a seasonal rotation of plentiful vegetables, there was a single meagre bowl of frozen peas to go between 500 children. Instead of freshly minced meat, he found an array of nastily pink turkey burgers and what Oliver himself has called "f***ing Botswanan free-flow beef". We all know the public outcry that ensued. Not since Upton Sinclair published his novel The Jungle in 1906, on the horrors of the Chicago meat industry, prompting Theodore Roosevelt to introduce federal meat inspection, has a cultural event produced such an immediate shift in government policy on public health. The result in Oliver's case was the £280m pledged to improve school meals and the acknowledgement at last from new Labour that "something must be done".

But the question remains as to why British school meals went so badly wrong in the first place. How and when did a service that was meant to be part of a child's education - providing for their bodily development while teachers fed their minds - get reduced, in places, to a morass of Turkey Twizzlers, chicken nuggets and potato smiley faces? Unusually, this is a question on which almost every expert agrees. When did the school meals service first deteriorate? 1980. How? The Local Government Act of Thatcher's first term of office.

The school meals expert Nan Berger has written that "the 1980 Act was a piece of political assassination calculated to destroy the school meals service". This undermined the nutritional content of school meals and the breadth of their provision. Until 1980, the price of the meals was fixed nationally. This gave a level of nutritional security, especially to children on free meals. In 1950, the price of lunch was sixpence; by 1969 it was one shilling and ninepence. But in 1980, the national price was abolished and replaced with any price the local education authority saw fit to charge. Given that LEAs had to bear the cost of subsidising free school meals, it was not in their interests to keep the price high enough to keep up quality.

The result was huge discrepancies in the price of school meals across the country that remain to this day. If you are a child receiving free school meals on the Isles of Scilly, your lunch will have cost £1.75, of which a generous 90p goes on ingredients (according to recent figures produced by the Guardian). By contrast, a child in Stockton-on-Tees is given a meal priced at £1.35, of which 39p goes on ingredients. Even allowing for the magic that a good cook can work with meagre ingredients, the chances are that the Scilly Isles child will have had a proper meal while the Stockton child will have had little more than a processed snack.

In 1978, the then secretary of state for education, Shirley Williams, told the House of Commons she would "deplore" any attempt to replace the school meal with a "snack meal that had nothing like the same nutritional value". But after 1980, this happened in many places, as several LEAs introduced "cash cafeterias" in secondary schools, some of which churned out low-cost burgers, chips and fizzy drinks to turn a quick profit. Many good cooks were made redundant, their skills no longer needed. (In 1981, Tim Lang calculated that the 1980 Act resulted in 30, 000 lost jobs.) How did the LEAs get away with this? Because the 1980 act abolished any minimum nutritional standards for school meals and did this in the name of "parental responsibility" and "choice". Things got even worse in 1986, when the Social Security Act withdrew provision for free school meals to half a million children. Worse still, in 1991 the Conservatives introduced "compulsory competitive tendering", which handed the contracts for school meals services to those who could do it cheapest - in many cases, the big private firms such as Scolarest, exposed on Jamie's School Dinners.

It is all very different from the 1944 Education Act, when a universalist system of school meals was set up, financed mostly by central government. This act required LEAs to provide a free meal to every child in a maintained school. Cooks were to work on the assumption that for many children this would be their only substantial meal of the day. Clear nutritional guidelines outlined the ideal balance of proteins and fats. School lunch, moreover, was to be seen as an integrated part of the school day. This was in contrast to the 1906 Education Act, which treated school meals not as a universal part of education but as a way of treating "needy" children who might otherwise starve. This left school catering tainted with a whiff of the soup-kitchen and a stigma that attaches even now to free school meals. The 1944 Act was designed to remove this stigma and make a wholesome midday meal - complete with Manchester tart or apple meringue pie - available to every child, rich or poor.

So far, in British history, there have been three philosophies of school meals: a charitable philosophy - the piecemeal feeding of the malnourished of 1906; a consumerist philosophy - the give-children-what-they-want-at-a-low-price-and-never-mind-if-they-become-diabetic-and-obese ethos of 1980, 1986 and 1991; and a universalist philosophy - the inclusive spirit of 1944. These are, essentially, the three models of how to treat children (especially poor children): as pitiable Olivers asking for more; as walking wallets; or as citizens deserving health and a dignified life.

As it enters its third term of office, it is still unclear what the government's philosophy is. In 1997, David Blunkett, then education secretary, lamented the way the quality of "school dinners" had deteriorated over the past 18 years, suggesting a universalist approach might return. But the messages since then have been mixed. Labour has increased the numbers eligible for free school meals, yet repeatedly declined to ban vending machines selling fizzy drinks in schools, as if Coca-Cola had a God-given right to worm its way into a child's education and teeth. There is still no clear connection between what is taught about food on the national curriculum and what children actually eat in the dinner hall. In 2000, the government gave schools the freedom to opt out of LEA provision of school meals, which has had good results - in schools such as St Peter's Primary in Nottinghamshire, where that inspired cook Jeanette Orrey introduced local and organic food; and bad results - in schools that signed themselves over to rapacious private contractors.

The National Fruit Scheme gives all children aged four to six a free piece of fruit every afternoon. But what of those over six? As on so many other questions, new Labour has tried to square a universalist philosophy with a consumerist one, with odd touches of charity here and there. The confusion isn't helped by the fact that school meals fall between three Whitehall departments - Health, Education and Social Security - all of which would see a benefit if only the government could reclaim the spirit of 1944, and make a decent, well-cooked school lunch a universal entitlement rather than a matter of chance.

Bee Wilson is a food columnist on the Sunday Times. She is writing a book on the history of adulteration