It is 10.30am on a dank day in Alloa and the P2 class of St John’s Primary are sitting at their desks slurping big, curvy slices of honeydew melon. As the juice runs down their chins on to their sweatshirts, class teacher Seonaid MacLean reads them a letter.

It is purportedly from the Food Dudes, a foursome of fearsomely healthy children whose task is to guard the world’s supply of fruit and vegetables from the evil grasp of General Junk and his fiendish friends.

The children have been enjoying their adventures on television for the past few weeks.

Harnessing the power of videos, peer pressure and bribery, the Food Dudes programme tries to change the way children eat. It turns the tables on junk food advertising and uses television to make apples and broccoli seem cool.

The structured programme, which was devised at Bangor University’s Food Research Unit (www.fooddudes.co.uk), introduces the idea of eating fruit and vegetables every day - the Food Dude heroes provide social models - and gives children the chance to taste them. It creates an environment which supports healthy eating and encourages children to see themselves as fruit and vegetable consumers.

In the Forth Valley - where the Scottish Executive food tsar Gillian Kynoch used to work as a community dietician - the health board, in partnership with Clackmannanshire, Stirling and Falkirk councils, has introduced nearly 2,000 primary children to the Food Dudes programme over the past two years.

The three-year project will cost pound;15,000 (about pound;10 per child) and has been financed by the Scottish Executive’s Health Improvement Fund.

At St John’s Primary, it certainly is having a positive effect.

“The tomatoes we had yesterday were sour,” says P2 pupil Stuart, “but the melon today is nice.”

Next to him, Chelsea is looking gloomy. “I don’t like it,” she says, “but I love strawberries.”

“I love kiwi fruit,” pipes up Zach.

In the P5 classroom, the consensus is that the Food Dudes videos are “a bit babyish” but the prizes of water bottles, pencil cases, pencils and rulers emblazoned with the Food Dudes logo (some of which they get for tasting fruit and vegetables while the bigger prizes are awarded for eating servings) have gone down well and the pupils queue up to fill in a fruit-eating chart with enthusiasm.

“Melon is gross,” pronounces Garry, but the programme has also introduced him to red apples and grapes, which he likes. “I get my mum to buy me bags of grapes now, green seedless ones.”

Connor has also rejected the melon but would give watermelon a try. “I’m good at spitting and you have to spit the seeds out,” he says.

“This was a very unadventurous class,” says Eileen Forrest, the P5 class teacher. “Last year we had an Egyptian picnic and they wouldn’t try dates or figs.” Now, six weeks into the nine-week programme, most of them will at least taste whatever fruit or vegetable is on offer and make up their own minds about what they like.

The staff avoid pressurising the children who don’t want to eat what is on offer. There will be something different another time.

St John’s Primary runs the programme three days a week, relying on the support of clerical and auxiliary staff and a rota of parents to come in and prepare the fruit, which is delivered by the Co-op.

Janette Wieczorek, the depute headteacher, says: “If there was the money, I’d be happy for this to go on every day.

“If you were to come back when today’s P3s are P7s, I would be able to say we’ve got a school of fruit and veg eaters.”

Raploch Primary in Stirling was one of the first schools to run the Food Dudes programme. A year on, the daily fruit trolley is still selling plenty for the pupils to eat at break time. A member of staff shops for the trolley twice a week.

“The children have really taken to the whole idea of eating fruit,” says headteacher Anne Stewart.

“It’s a slow process, educating the tastes and habits of a lifetime but I would hope the kids are going to get healthier.

“We’re trying to get at the parents through the kids.”

“There is a lot of good will for the programme in schools and catering,” says Anne Clarke, the community dietician who has been running Forth Valley’s Food Dudes programme for a year.

“Teachers are very skilled at getting a message across. If they take this on board, it could make a real difference. It has to be sustained over time.”

Food Dudes is not the only approach to promoting healthy eating that is being tried in Falkirk. At St Andrew’s Primary, under the cheery logo of an octopus and the catchline “Eat Ollie Your Dinner” (designed by a pupil), the dining room is buzzing with lunchtime activity.

The kitchen staff wear smart white chefs’ jackets, brightly chequered aprons and baseball caps. There is new furniture and display counters and the atmosphere is a world away from the dreary dining hall of years past. But it is not only the ambience that has changed; so has the food.

Today, two kinds of pizza, spaghetti Bolognese, garlic bread, macaroni cheese, chicken nuggets, baked beans and potato waffles are being served.

School macaroni can conjure up terrible memories but this is deliciously smooth and tasty, and with a side salad it makes an ideal lunch.

As well as hot food, across the corridor in the gym hall a second gang of pupils is choosing from the pick and mix sandwich bar. With special paper sacks in hand, the children have to make some difficult choices: a variety of sandwiches; a piece of home baking or a packet of crisps; some fresh fruit or a yogurt; a fruit drink, flavoured milk or mineral water.

St Andrew’s is one of three Falkirk primaries taking part in a pilot project to increase the number of pupils eating school meals, to raise their consumption of bread, dairy products, fish, fresh meat, fresh fruit and vegetables and to decrease their consumption of sugar products. The other schools are Stenhousemuir and Grange, but St Andrew’s has been the most successful. Its uptake of school meals has increased from 30 per cent to 66 per cent of the roll of 370 pupils.

The transformation has been brought about by Catering Way Forward, a partnership between Falkirk Council’s corporate and commercial services, which are responsible for catering, and its education services.

Surprisingly, the departments had never before jointly discussed school meals.

Mirren Begbie, the policy initiative manager for Falkirk’s education services, is delighted with what is going on in Ollie’s Diner at St Andrew’s. “It’s ideal. It all works really well,” she says.

Dorothy Graham, the building services officer, says: “More children go out to eat with their families now and they know what’s available. We’ve got to reflect something of that.”

Mrs Begbie agrees and the partnership has continued to survey children on what they would like. She reels off some ideas: “Themed days, coloured plates, more pasta, salads and vegetarian options. They want to be able to eat outdoors in summer, which had never occurred to me. But why not? We have to ask how we can make the whole experience more pleasant for them.”

John Evitt, the headteacher of St Andrew’s, appreciates the difference a good lunch makes to his pupils and staff. Until 2000 the school meals were made at Graeme High and transported to the servery kitchen at the primary school (a five-minute drive).

“When meals are transported, well it depends how far they are transported; but when food is cooked on the premises, the aroma - and here it is good - wafts through the school and everybody looks forward to lunch,” he says.

Primary 7 pupil Alison Hughes certainly approves of the change. “When the food came from the high school sometimes it was cold. It’s much better now.

There are much better choices,” she says.

Some elements of Ollie’s Diner have been rolled out to all Falkirk primaries but the full package is too costly to be undertaken immediately.

Work on the kitchen and dining area at St Andrew’s cost pound;30,000.

However, three schools will be fully upgraded this year.

Free brown and tomato sauce is now the rule authority-wide: with a squirt of sauce available, a child is apparently much more likely to eat both hot dog and roll. The project report shows that consumption of fresh fruit, yogurt and fresh red meat has risen markedly in all three pilot schools under the new regime. There has been less impact on vegetables and fish.

At St Andrew’s, Siobhan Harkins is waiting behind her P2 class for spaghetti Bolognese and salad, while a boy in front of her swithers between fresh fruit and a Tunnock’s teacake.

“Go on, have an apple,” says the flamboyant lady behind the counter.

Against the odds, he does.