Standing under the old oak tree at Styal, we look slowly round at an archetypal village scene: a field, a chapel, a pond, a row of ancient cottages. But then the 20th century comes into the frame, in the shape of a group of secondary-school pupils, all blue uniforms and clipboards.

“If you had 10 groups like that walking past your window every day, how would you feel?“asks the National Trust’s countryside education officer Gareth Binns.

For most of these two dozen 13 and 14-year-olds from St Paul’s High School, Wythenshawe, living on a Manchester housing estate, the countryside is unfamiliar territory. So this fieldwork trip to a popular National Trust property is invaluable in helping the school to cover the environmental element in the national curriculum, where students need to learn about the conflicting demands made on scenic attractions, how they are planned and managed, and how considerations of sustainable development, stewardship and conservation affect such planning.

Today the St Paul’s students are getting a glimpse of how the National Trust deals with these large questions in practical terms in the real world, for Styal Country Park and the adjoining Quarry Bank Mill are among the most visited of the Trust’s properties, attracting around 350,000 people a year, 60,000 in school groups.

Styal village, one of the few remaining unaltered factory colonies of the industrial revolution, is part of the estate. Maintained by the Trust, it is now just an ordinary village, though a most attractive one. Previously an agricultural hamlet, it was expanded 200 years ago by Quarry Bank’s owner Samuel Greg, to house his mill workers. It has a shop, cottages, two chapels, and a school.

The village is just one of several stopping-off points during the students’ slow trek around the estate. At each halt, Gareth Binns invites them to look round at the landscape, and consider how successful the trust has been in balancing the need to improve access with that of protecting its unique features, as well as the needs of local people.

The students have paused under the oak - but well away from the cottages - to carry out a short landscape and environmental quality survey, considering questions such as noise-levels, litter, vandalism, the density and age of the buildings, and the types of landform and habitat nearby.

Gareth Binns points out various ways in which the Trust has tried to preserve the distinctive unspoilt nature of the spot: no signs or information boards, no picnic tables - and definitely no allowing the cottages to be used for holiday lets. “We want to keep this place like this for ever,” he says.

While the group fill in their questionnaires, there’s a lively discussion about the control of dogs and the rights of their owners, and the limits on drivers of off-road vehicles, whose machines create noise, pollution and unwelcome ruts along muddy country lanes.

These are two issues which stir up the Trust’s membership. “But I don’t want you to think that there’s nothing but conflict in the countryside,” Gareth says. “It’s just that it is rather more than a nice place to look at; it’s got people using it, people living and working here.”

Half a mile on, and there is no one in the steep wooded valley of the River Bollin near Quarry Bank, originally the private pleasureground of the Greg family. These days a team of wardens look after the woods, planting trees, and repairing bridges, paths and river banks.

Erosion is clearly quite a problem. In one clearing thousands of visiting feet have eroded the river bank, and hugely broadened out the path above, despite the presence of stone steps. “But maybe the erosion is OK here as long as the other paths are not too bad,” suggests Gareth.

The day ends back at the car park. The students look at its design and capacity, consider how alternative means of transport to the site can be encouraged, and generally ponder on how parking can be used to control the number of visitors.

Seamus MacAuliffe, St Paul’s curriculum coordinator, is delighted. “With some of these kids, unless you put them into the actual situation, they’ll never understand these kinds of ideas. But this trip has made them very concrete .”

A test of his judgement comes a week later, when the students take part in a decision-making workshop in Manchester Town Hall, where some of the same issues are being debated by 200 grown-up delegates at the National Trust’s centenary countryside conference.

Students study the site map of an unnamed trust property (actually Dovedale in the Peak District), consider how best to spend a (paper) budget of Pounds 250,000 and discuss issues from disabled access to dog loos.

By the end of it, Gareth says afterwards, “Some of them are becoming quite sophisticated in their thinking, and beginning to think about matters such as zoning, or asking visitors for their views. I think they see better the value of a place like Styal, and want to be involved in decision-making about its future.”

o Further information from Gareth Binns, National Trust, 36 Queen Anne’s Gate, London SWlH 9AS. Tel: 0171 222 9251

Jonathan Croall is the author of Preserve or Destroy: Tourism and the Environment, published earlier this year by the Calouste Gulbenkian Foundation (Pounds 6.95)