The boy on the bus to school can’t wait to find out what’s for lunch. He flips open the plastic box on his lap and examines the contents. “Oh no, not again!” he groans, “Yuk! Every day it’s the same.” Then one day he opens the box, punches the air and shouts out “Yes!” What can have got his taste buds so excited? A salad sandwich, low-fat yoghurt and an apple? Not likely. He’s delighted because his Mum gave him a Dairylea Lunchable, the cracker, processed cheese-and-meat snack that, the television advert says, “puts the fun time in lunch time”. The message is clear. Parents, if you want your kids to be happy, pack them off to school with a Dairylea Lunchable in their box.

Not everybody agrees. The Parents Jury, a 1,500-strong lobby group of mums and dads concerned about children’s diets, voted them in 2002 the “worst food targeted at children’s lunchboxes”. Other targets of their anger included the sugary Kellogg’s Fruit Winders and Procter and Gamble’s Sunny Delight drink.

School dinners have been the subject of derision for years, but lunchboxes - the midday meal of about half of Britain’s schoolchildren - have escaped the same scrutiny. Late last year, the Food Standards Agency released its first survey on the subject, which looked at the lunchboxes of 556 children from 24 primary schools. Only one in five met the minimum dietary standards required of cooked school dinners. The most popular item was a white bread sandwich (found in 87 per cent) followed by crisps (71 per cent) and a biscuit or chocolate bar (60 per cent). Less than half contained a piece of fresh fruit.

In an average lunchbox, children were eating twice their recommended daily allowance (RDA) of sugar and nearly half that of salt as well as high levels of saturated fats. Health campaigners say adverts, now under fire from the Government, aimed at children make snacks, crisps, sweets and drinks look nice, but don’t mention the long-term effects of too much fat and salt.

Packed lunches have become the new battleground. On one side are health campaigners, the Government and parents. On the other are the manufacturers vying for a share of an industry worth an estimated pound;4.1 billion a year. And they are giving ground. Kraft, for example, last year reduced the salt content of Lunchables from an average of 2.5 to 2 grams, though this is still two-thirds of the recommended daily allowance for a six-year-old . Schools are stuck in the middle - wanting to make sure their pupils eat healthily, but unwilling to tell parents what to put in their children’s lunchboxes.

You might think Cornwall had a head start when it came to wholesome packed lunches - it is, after all, home of the pasty, one of the original healthy convenience foods, packed with protein, carbohydrates and vegetables. The Cornwall Food Zone, set up by the county’s education authority and medical professionals to improve pupils’ understanding of what they eat, has introduced colour coding (a green apple one day, a yellow banana the next) and a rewards system for those bringing in nourishing lunches. Nevertheless, it describes the task of making packed lunches more nutritious as “perhaps the biggest challenge schools will face”.

The experience of Penzance infants’ school - awarded healthy school status last year - is typical. Having successfully introduced the 150 children to previously unheard of pursuits such as t’ai-chi, they have found it harder to change parents’ shopping habits.

“Even when the children are eating fruit in school and asking their parents for fruit, their parents still don’t buy it,” says Sarah Penberthy, the healthy schools co-ordinator. In a relatively deprived area, food that is cheap and convenient is top of most parents’ shopping list. But Penzance infants is determined to press on. Fizzy drinks and sweets are banned and teachers are “trying to educate parents” about cheap and healthy alternatives, she says.

At John Hellins primary school in Potterspury, Northamptonshire, they have introduced a healthy snack policy in the hope that it will influence lunchtime eating. “It was a process of consultation - we didn’t want to feel that we were killjoys,” says the headteacher, Mike Langrish. “We quizzed children for ideas about what was good fun to eat and what was good for us health wise.”

Mr Langrish devised the policy in consultation with senior staff, the school nurse and local health authority. Mindful that similar schemes had met with parental resistance, they asked pupils to devise a questionnaire on banning sweets and crisps at break time. The response was “remarkably positive”. Since then, the school has extended the Government’s free fruit scheme for four to six-year-olds to all pupils, and parents have been amazed by the change in their children’s eating habits.

“They are saying to me: ‘I can’t believe it - they are walking round eating raw carrots and cucumber’, ” says Mr Langrish. An unexpected bonus is that John Hellins has solved its litter problem as discarded fruit peel and apple cores are put on the compost heap.

Brenda Bigland, headteacher of Lent Rise primary in Slough, one of four beacon schools commended for healthy eating, tried selling the notion of nutritious packed lunches with that old marketing ploy: the competition. Children discussed what was and wasn’t healthy and designed their own ideal packed lunch. The winner in each class received an award and a Harry Potter lunchbox.

“We didn’t have a lecture or a lesson on what a healthy lunch is - it was an exploration,” she says. “We throw them a problem and say: ‘What’s the solution?’ That was the idea of making a packed lunch - how do you sell this to someone else, how do you make it attractive to eat?” Joy Tagg, head of Moorings Way infants in Portsmouth, another beacon school for healthy eating, gets the message across with regular, gentle reminders. “I try to drop the idea of a healthy lifestyle and particularly a healthy diet into all areas of the curriculum,” she says. Singing “Hot Cross Buns” might lead to a discussion about whether they are good for you or not. She invites parents in once a term for a family lunch, but doesn’t impose lunchbox dos and don’ts. “It’s a bit of a cheek telling parents what to put in their kids’ lunchboxes,” she says. “If we can encourage them and the children to think of the healthy way of doing things, then we will get there much quicker.”

Giving parents and children an informed choice is the best way to combat food advertising, says Annie Seeley, the Food Commission nutritionist who co-ordinates the Parents Jury. The commission is one of 85 organisations backing government moves to protect children from the promotion of foods that contribute to a poor diet.

“A lot of people don’t know that a bottle of Coke has 10 teaspoons of sugar in it,” she says. “But if they did, they might not buy it. Children’s advertising shows unhealthy foods in the best possible light - associating fatty and sugary foods with popularity, happy playground relationships and sporting success. Food companies are experts at selling junk food and soft drinks to children using advertising, packaging and free gifts, but the one thing that repeatedly gets left out is good nutrition. ” Meanwhile, schools have the job of convincing pupils and parents to take the healthy option. So long as they don’t know any better, the boy on the bus - and the thousands like him who take their lunch to school - will continue to crave food that’s bad for them.

A WEEK IN A LUNCHBOX

MONDAY

Portion of tuna (in brine), sweetcorn salad, currant bun, apple, bottle of flavoured milk

TUESDAY

Three mini pitta breads filled with chicken salad and low-fat mayonnaise, pack of three small chocolate-coated sponge cakes, one satsuma, bottle of flavoured water

WEDNESDAY

Small slice of deep-pan pizza with ham and pineapple, low-fat strawberry yoghurt, four cherry tomatoes, pear, bottle of fizzy water

THURSDAY

Peanut butter bagel, cereal bar, peach yoghurt drink

FRIDAY

Mixed veg and rice salad, packet of reduced-fat crisps, chocolate muffin, bottle of chocolate-flavoured milk

Food Standards Agency: www.foodstandards.gov.uk newsnewsarchivelunchbox `PACK ‘EM IN

* Meals need different tastes, textures, shapes and colours to maintain children’s interest. Some Cornish schools use a colour-coding system.

Pupils bring in an item of a different colour every day, for example, a green apple one day, a yellow banana the next, and so on.

* Try a traffic-light system in which foods are labelled as green (eat lots), amber (eat in moderation) or red (be careful). Kitchen staff encourage children to go green.

* Reward and congratulate those who bring in nutritious lunches. This encourages healthy eating as young children are unlikely to truly understand the benefits of a good lunch, but do understand praise. Make the idea of a healthy lunch exciting. But don’t use sweets or chocolate as the reward.

* Consider holding workshops or road shows, themed days and assemblies focusing on diet and keeping healthy. Or a technology week where pupils, teachers and parents work together to design and make a packed lunchbox.

* Ethos is important. Where children eat and the opportunities they have to eat lunch are critical. For example, cutting break times may only lead to pupils not having enough time to eat a proper and healthy meal.

Tips from the Cornwall Food Zone: www.cornwall.gov.uk Educationfoodzonedefault.htm

PARENTS CAN...

* Before you add a new food to a lunchbox, try it with your child at home.

* A taste can be as small as half a teaspoon.

* Only offer one new food at a time.

* Children are more likely to try a new food if they have the option of not swallowing it. Show children how to carefully spit out the food into a tissue if they don’t want to eat it.

* Continue to offer nutritious foods.

* Have reluctant food tasters sit with an enthusiastic friend.

* Serve an unfamiliar food with familiar ones.

* Children prefer brightly coloured foods with mild flavours and interesting textures.

Tips for parents from the British Nutrition Foundation: www.nutrition.org.uk