Close to Gatwick airport and under several flight paths is a small patch of woodland, just a 10-minute drive from Thomas Bennett Community College in Crawley, West Sussex. "It's a tatty wood, but we like a tatty wood," says Tina Hutchinson, a maths teacher and the person behind the secondary school's forest programme.
"It's good for them to get a bit dirty and expose them to what's out here," she says, above the din of 12-year-olds racing around, trying to be the first to find a sycamore leaf.
"We had a boy - he's in Year 11 now - who came camping with us last year," she says. "He was standing over the other side of the field shouting at me: `Miss, Miss! Look, look!', pointing to the woods near the South Downs. As I rushed over to him, asking `What's the matter?', I saw a rainbow. He said: `What's that?' as if it was a spaceship or something. He'd been taught about rainbows and would have seen them in books, but he'd never seen one for himself."
A growing awareness of the importance of sustainability and the environment is placing more value on forest schooling. It is no surprise that the idea originally came from Scandinavia, where there is a natural abundance of woodland.
They started in the UK in the 1990s, but the Government's 2006 Learning Outside of the Classroom manifesto gave teachers more encouragement to get involved: 100 forest schools in England and 20 each in Scotland and Wales were recorded in 2006, and since then many more teachers have undergone training.
Most forest schools are for very young children, whose formative development is believed to be enriched by outdoor learning. The concept was established as a kindergarten programme in Denmark in the 1980s.
Recent research carried out in Wales and England by the New Economics Foundation found that children who took part in forest school activities gained greater self-confidence, the ability to work in a team, more motivation to learn, and pride in their surroundings.
Also, dealing with the demands of the outdoors and taking part in camping activities are increasingly being shown to benefit children who have special educational needs. In fact, Thomas Bennett College's forest school was shortlisted as an outstanding special needs initiative in last month's TES Schools Awards.
The school set up its forest visits three years ago, not only to teach pupils about nature, but also to provide an alternative environment to traditional school. They were started specifically for pupils who were at risk of exclusion, often because they had no aspiration or their learning and behaviour difficulties made traditional school a challenge.
Forest schools are said to be as much about a holistic ethos as a physical space. Mrs Hutchinson, a former head of department, and Mary Peach, her colleague, were attracted by how easy and relatively cheap it was to organise activities that could have such an impact.
Mrs Hutchinson has also found the forest school is a "liberation" from mounds of paperwork and a restrictive curriculum. "It is education - not just mucking about in a wood," she says.
"Part of getting used to the environment is risk taking, which forms an important part of the pupils' development."
This drizzly Friday afternoon, a small group of 13-year-olds who are regular visitors to the camp are guiding a Year 7 tutor group on a taster session. The older pupils are proudly showing off the hammers they carved and the home-made oven where they cook pizzas. They have made a campfire and settle down to listen to a story while toasting marshmallows.
"One of the reasons we read a story is that these are children who don't listen to anyone," says Mrs Hutchinson. "But once they have had something to eat and are in front of a fire, they are much calmer."
About two-thirds of the pupils at Thomas Bennett College are on the special educational needs register and a third of the Year 7 pupils are unable to read or write when they start at the school.
This is Linda's (not her real name) first time in the forest and she wants to come back. "I'm kind of quiet in class," she says. "In school, if you say something wrong, people laugh sometimes. But out here, if you say something wrong, no one cares and no one laughs, because not everyone knows everything."
This is also the first time that Shohreh Bayram, the Year 7 class's tutor, has been to the forest, but she is well aware of the impact it has had on individual pupils. "When they come and talk to you about their visit and what they have done, children who usually don't have any confidence in the classroom are really proud," she says. "It's amazing to see the transformation. They seem so confident."
Amanda Jackson, director of the school's learning and support department, co-ordinates about 40 full-time teaching and support staff and a range of classes, from lessons in self-esteem to outreach projects with the fire service. "What is most important about the way (forest school) is done here is that it is embedded into the curriculum," she says.
Tutor groups go for a taster session to bond, and pupils with special educational needs are timetabled to have a few sessions a week in a 10- week programme. The teachers involved are proud of the way the forest school has been perceived by the pupils. "It's seen as OK to go; not like a slow learners' group that they would be embarrassed about," says Miss Jackson.
At first, parents were dubious about what their child could gain from scheduled time in the woods. "It is difficult in this educational climate," says Miss Jackson.
"If my son or daughter is in the forest, they're not doing their English, maths and science," she says.
"Some parents do initially have reservations and concerns, but once their child is on the programme, they become happier because their child is obviously happier."
It has been hard to show any improvement in academic achievement as a direct result of forest school, partly because of the range of support given to the pupils who attend the sessions. But an evaluation of pupils' progress at forest school from 2006 to 2007 by Xavier Eloquin, the school's education psychologist, found that the scheme has resulted in fewer exclusions, raised attendance and improved self-esteem among vulnerable pupils.
"It has been moving for me, as an outsider, to see previously disaffected and demotivated pupils getting on with their allotted task and taking real pride in it," says Mr Eloquin.
"Socially, a lot of time is spent around the fire, brewing tea, cooking, carving, whittling and telling stories. As a psychologist, I am struck by the way in which this more natural environment allows things to happen more organically and without any social skills sessions."
Rudolf Steiner schools have a history of endorsing outdoor play for learning. Camphill School, on the outskirts of Aberdeen and near the River Dee, applies the Steiner-Waldorf education principles, with an emphasis on imaginative play, in a therapeutic way for children with special needs. The city council funds its Nature Nurture project, where under-fives who are identified by social services as being at risk are taken into the local woodland by trained Camphill School teachers.
Terri Harrison, a teacher, who helps to lead the programme, says: "This is specifically a therapeutic programme that works with the benefits of being outdoors. The kids are severely traumatised and have very delayed development, movement and speech. The youngest is only 18 months old."
Like the forest school programme at Thomas Bennett College, the Nature Nurture sessions follow a similar format each time. "The things that are important to us are repetition, a slow pace and the fact that sessions are child-led," says Mrs Harrison.
"Every single transition they make, even from different rooms, is potentially traumatic, so we also sing songs to flag up what's going to happen."
The projects currently run for 10 weeks at a time to maximise the number of children involved. Even over this short period, Mrs Harrison has been amazed at the results that are achieved in terms of the children's emotional, cognitive and physical development.
At Thomas Bennett College, Miss Jackson acknowledges that teenagers aren't as quick to change. "The results have been a long time coming. As with anything, it doesn't happen overnight," she says. "To change that ingrained, learnt behaviour takes time."