We are in a clearing in the North Wood of Pollok Country Park on the south side of Glasgow. If you concentrate, you can pick up the low hum of traffic on the M77 motorway, but to all intents and purposes the 12 pupils from Govan High School's autism unit are in a haven, sheltered from the cold winds of the outside world by sycamore, horse chestnut, beech and elm trees and warmed by the fire they have built.
But this haven is also a classroom in a Forest School, part of a growing trend whereby children go into the woods as a learning experience and build shelters, make fires and care for the environment.
Children who would normally spend their spare time staring at electronic consoles appear content to wander through trees and gather wood. The bickering that has punctuated the journey has almost ceased as the group breathe in, exhale and relax.
At any one time in Britain it is conservatively estimated that more than 60,000 children are escaping into forest classrooms, usually for half a day per week, to improve their health, social skills and confidence.
Sally York, the education policy adviser to the Forestry Commission, which is behind the trend and is running sessions for children aged three to 18, believes that educational experiences shouldn't be limited to the classroom: "Learning happens all over the place," she says. "Teaching happens in space and that space can be indoors or out."
The move to outdoor classrooms addresses a number of issues; childhood obesity, sustainability and the environment, according to York. "Forest schools are teaching children about sustainable development and connect with all areas of the curriculum. They can also help with those important skills impossible to teach, such as socialisation and communication."
The literacy specialist and author of Toxic Childhood, Sue Palmer has studied the benefits of Forest Schools in Scandinavia where the idea originated. "In Denmark, the Forest Schools tend to be kindergarten – for children aged three to seven, and they are there all day, every day. Here it tends to be a day or an afternoon."
Palmer favours the Danish approach but, even though she believes we are introducing British children to the outdoors too late and for too short a period of time, she still thinks it is a step in the right direction.
"I have to admit a couple of hours are better than nothing, but children today are getting out and about so little, it's really just a drop in the ocean."
Education's target culture, where the emphasis is on pencil and paper subjects, increasingly pushes these opportunities outside the curriculum, she says.
"It is no surprise that the countries which were at the top of the UNICEF survey of childhood wellbeing were the Netherlands and the Scandinavian countries, where children are outdoors much, much more than in the UK. Children here aren't even walking to school."
Only a handful of British schools have fully embraced the Danish model, the Secret Garden Outdoor Nursery in Fife being the first. Its founder, Cathy Bache, has been taking three- to five-year-olds out for six years, first as a childminder, then as a registered nursery. In that time she has never kept the children indoors due to the weather, even in the freezing temperatures of this winter. "We take the children out into woodland near Cupar, which has a mixed terrain, with different types of shelter. We chose the best location for the weather that is forecast that day. She adds: "There is a Norwegian saying, 'There is no such thing as bad weather, only bad clothing.'"
Bache, who has 35 children in her charge, believes the greatest benefit is that they are fitter than their peers. "Children have the most physical and emotional resilience imaginable and we have taken this away from them," she says. "The Forest School children develop physically in a manner that children in a more cocooned life don't, and have been fulfilled spiritually and emotionally."
Pupils from her nursery don't struggle when they attend the more structured regime of a primary classroom, because local primaries have adopted the Forest School model, she adds.
Today's task is to build a fire. The children are organised by group leader Ali Horning, who asks them for suggestions on the best method of chopping wood and building a fire that will be safe for everyone. They start to chop branches into pegs and kindling.
Working in pairs, one holds the axe in place while the other brings a mallet down on top to split the wood. The pupils are more confident doing this than their teachers; as one pupil lurches towards the axe, a protective arm comes across from one of the accompanying adults.
But this element of risk is essential, according to Sue Palmer. "If you eradicate all risk from children, they won't get anything out of the experience," she explains. "Unless you do things for yourself, you won't learn how to make your own risk assessments."
She adds: "By talking about risk to children we are imposing an adult attitude; to a child it's just exploration. They have to be able to make a judgement based on the knowledge of what they can do, and if they don't use that exploratory gene at an early age, then they are not going to be able to assess risk."
However, in a gesture towards our germ-free culture, Horning has brought some wet wipes.
Each child gets something different out of Forest School. Asked what he gets out of it Luke, 12, says one word, "freedom". After a moment, he adds: "There is no excitement in the classroom but I'm learning how to be safe here and do things I'm interested in."
Another 12-year-old, Craig, enjoys being outdoors. "Sometimes you see birds," he says. "One time I saw a robin – something I've never seen before."
Stefan, also 12, likes using the tools to chop wood. "I've never held an axe before," he says. "I was pretty surprised Ali let me use it as not many children are allowed to." Stefan finds that walking through the woods makes him feel calm. "There's nothing to be scared of when there is someone there looking out for you."