I t has often been said that art is a window on society, and that is certainly the case at Crispin school. Stroll with Richard Horsham, the head of art, around the various creations with which he and his pupils have adorned the grounds, and a pattern soon emerges. Here is a dragonfly sundial made out of recycled steel, and there is a collection of novel seats fashioned from old railway sleepers.

One piece of sculpture combines a living rowan tree with reclaimed timber from derelict canal lockgates, while the giant seedpods that decorate the entrance hall are made from yesterday’s newspapers and chicken wire salvaged from a local apple orchard.

So consistent are the themes of sympathy with nature, the re-use of materials and engagement with other people (many of these works were made by entire year groups) that a visitor who knew nothing of this comprehensive school in the Somerset town of Street might guess that it had a particularly strong commitment to education for sustainable development.

And they would be right.

Paul James, who recently took over as head, is a zoologist by training, and he had some idea of what to expect when he arrived. “But,” he says, “you have to be here to understand how ESD permeates the culture of the school.”

He recalls his job interview, and how he faced challenging questions from a panel of pupils as part of the selection process. “Our young people leave here with a real sense of what ESD means,” he says. “And it isn’t just about the environment. It’s also about global citizenship and encouraging leadership, pupil participation and democracy.”

At Crispin, ESD comes from many directions. Thanks to support from the WWF, children learning maths might find themselves investigating oil-spill scenarios, while modern-languages students will conduct conversations about global footprints with counterparts in France and Germany. At regular intervals, the formal curriculum is suspended so that pupils can get out into the community and explore sustainable buildings, learn about water, or study waste management in the real world.

Crispin also has close ties with a school in the Kenyan village of Masana, and this involves exchange visits, economic co-operation and the sharing of ideas about sustainability.

And then there are the school council, the green committee, the recycling group and the fair-trade cafe, all of which provide opportunities for children to turn theory into practice.

Monica Allfrey, one of Crispin’s two deputy heads, sums it up. “It’s very difficult to pick out the bits that you might label ESD,” she says, “because there’s so much going on.”

Monica recalls her own “moment of revelation” when she was taking part in a WWF training weekend almost a decade ago.

“We had been talking about the social environment and bemoaning the fact that, while faith schools have a ready-made set of values which parents buy into, there is no self-evident set of values that everyone shares at a ‘bog standard comprehensive’. And then it struck me that, actually, there is.

Because how can anybody say that they are against sustainable development?

“Nobody can possibly say they think that stewardship of the planet, so that our great great grandchildren have something to inherit, is a bad thing.

Nobody can possibly say they don’t think it’s advisable to educate young people so they can participate. So once you understand that ESD is about sustainability in its very broadest sense - the way in which people engage with each other and with the physical world - you can see that you do have a set of values that speaks for itself.”

Monica was not alone in her enthusiasm, and soon, staff at Crispin were lobbying governors for an ESD co-ordinator’s post.

In that role, science teacher David Heath has found that he can use ideas and resources gleaned from WWF to “tweak the curriculum” in ways that enthuse students and enable staff to teach ESD without increasing their workload.

He said the school had found Pathways, the WWF’s planning framework for school sustainability, “a brilliant tool to use in teacher training. You can really switch people on to sustainable development, and I can see how it could be used quite easily by anybody, whatever stage they’re at, with a bit of support from the head and the senior management.”

And that is precisely what they have had at Crispin. Assistant head Frances Thomson was made responsible for pupil participation, and the results of the school’s collaborative style of leadership are tangible.

With a new environmentally friendly classroom block recently completed (it is named the Masana Building, in honour of the school’s Kenyan partners), pupils are now involved with a landscape designer in creating an adjacent peace garden. One group is researching more efficient alternatives to the smoky kerosene stoves used by many Kenyans, while another considers ways of marketing shoulder bags made in Africa from recycled denim.

Recently, David Heath has introduced pupils to the notion that discos, proms, year books and the fair-trade cafe might be run as student co-operatives, and the school council, whose members helped to interview the new head, has even had a say in the redesign of the school uniform.

“It’s all real decision-making - real hands-on stuff,” says Mr Heath.

Richard Horsham, under whose guidance students have been so successful at using reclaimed materials to turn their school grounds into a living sculpture park, has a personal theory about the origins of Crispin’s ESD ethos. He believes that it all started when a former head of humanities decided to dig a pond as a way of revitalising the school environment.

By all accounts, the project captured the imaginations of students and staff alike, to the extent that images of dragonflies and their nymphs appear everywhere at Crispin.

But whether or not Mr Horsham’s creation myth is accurate matters little.

For the fact is that the values expressed in the public art now permeate the curriculum so thoroughly that their influence can be felt in virtually every area of school life.