In the middle of a field strewn with daisies, Theo, 4, Alice, 4, and William, 3, are playing trains. They run along a narrow plank balanced on several old tyres that bounces as they jump on it, making chuffing noises and screaming with laughter when they lose their balance and fall in a heap.

Nearby, Ethan, 4, has wound double-sided sticky tape around himself and is rolling in the grass trying to get daisies to stick to him. Millie, also 4, clutches a piece of wood that she has selected from a pile and drawn on in coloured crayon. All over the field small groups of children are playing, running, shrieking, laughing and enjoying the bright spring sunshine.

This is not just playtime. This is the Farley Outdoor Learning nursery in Wiltshire, where the classrooms are invariably empty and the children spend all day, every day, outdoors – even the babies, who, at six months, entertain themselves in the sandpit or, when it is time for a nap, fall asleep gazing up at the sky in a series of sturdy Silver Cross prams parked in the courtyard.

And while today is sunny, Sue Palmer, the school’s principal, assures me that the children are outside whatever the weather, even in the rain and snow. “The best thing in the world is a huge downpour, because you get your coat on and you’re jumping around in it,” she says. “With us the children get wet and they get covered in mud – and they love it.”

Farley is one of a handful of nurseries springing up with an emphasis on getting children outdoors – all of the time. Inspired by Scandinavian principles they offer a fresh-air education where children learn by exploring the world around them. And more parents are starting to accept that the great outdoors is not the risk they thought it was – Farley is booked up until 2011. James and Michelle Kirkman even moved to Wiltshire from London when they heard the school was opening, so impressed were they by its ethos. “My kids are now outside all the time and I think that’s fantastic,” says James, an accounts manager. “It’s a brilliant way of life.”

The Kirkmans are part of a global movement of people who are starting to realise that keeping children cooped up indoors all day simply isn’t healthy. This summer, a book that has been a hit in the United States will reach Britain’s bookshelves, emphasising the urgency of “reconnecting” children with the natural world.

Richard Louv, author of Last Child in the Woods, has even coined a term for what is happening to our children – “nature deficit disorder”. He is a firm believer in the benefits of outdoor schools, emphasising that exposure to nature can improve health both physically and psychologically. He even argues that being outside all day makes a child more clever and creative too. “Natural settings stimulate learning,” he says.

But not everyone is convinced. Some believe that children can only learn properly when they are inside in a classroom, for example. “I’m all for children going outside in order to play and let off steam, but I think if you are learning anything that involves concentration and focus then it’s probably better for them to be indoors,” says Chris Woodhead, the Sunday Times columnist and former chief inspector of schools. Focusing too heavily on unstructured play, as many outdoor nurseries do, is a “recipe for ever greater undereducational achievement”, according to Woodhead. Instead we should be challenging children to learn beyond what they think they can, rather than just letting them go at their own pace.

Meanwhile there are those who question whether, in blizzards and howling gales, little ones should be outside at all – however well wrapped up they are. At the Secret Garden Outdoor nursery in Fife, Scotland, for example, there’s not even a building, and children as young as two are outside tramping the woods all day, even when it’s sleeting with rain. “We have a tent with a stove in it that we’ve had up through the winter and round the woods we have tarpaulins to protect us from the really teeming rain,” says its founder, Cathy Bache, who started the school in 2007 after four years as a child minder.

Bache is adamant she is doing the right thing. “Children don’t get enough space to play and they don’t get enough time to be,” she says. “Put in the woods you have the opportunity to give them that space. If they want to sit under a bush for half an hour, they can.”

The government certainly seems to be waking up to the idea of taking children outdoors – the Scottish Care Commission has been extremely enthusiastic about the Secret Garden, and in England, Chelsea Open Air nursery school, which opened in 1928 as a pioneer in outdoor education, is so highly respected that Ofsted, the educational watchdog, described it as a “magical kingdom”. At local level meanwhile, many councils are starting to send their teachers on Forest Schools training, which equips them to take children outside to light fires, build dens and, in many cases, just learn how to play.

“I worked with a group of children of eight and nine the other day and they’d never done den-building, they didn’t want to get their clothes dirty and they didn’t know what bugs were – they didn’t know how to play,” says Sarah Blackwell, director of Archimedes, an organisation that provides Forest School training.

It’s a deep-seated issue, agrees Kathryn Solly, principal of Chelsea Open Air nursery. “There was a withdrawal from the outside, and now we have children who don’t develop their lung and heart capacity and are sometimes obese. We’ve created a problem for ourselves that now we’ve got to find a solution for,” she says.

The answer, says Palmer, is allowing youngsters to take risks. “Our children are allowed to go and pick berries – there are stinging nettles and holly bushes,” she says. “We give them old planks and tyres to play with, they are out of sight of us some of the time and they play and learn and they actually keep themselves safe.”

According to Palmer this is what makes a happy child. “The children are the healthiest you could wish to meet,” she says. “We have no allergies, very little illness, their speech and language is far more advanced than others of their age because they’re outside doing things and learning to be independent. It is truly amazing.”

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