Few agencies or publishers have had such a profound impact on environmental education in schools and colleges as WWF (previously known as the World Wide Fund for Nature), which has just celebrated 15 years of producing materials for the educational market.
While other environmental agencies have all come up with high-quality publications, some teachers and inspectors say none can match the range and diversity of WWF's output, which now extends right across the curriculum, often into areas not normally associated with environmental work.
Much of the appeal of the list lies in its underlying philosophy. "WWF is one of the few publishing bodies that promotes the message of One World, and that's very refreshing," says Patrick Bailey, senior teacher at Loughborough University. "So many books at this level still offer a Eurocentric or even just Anglocentric view of the world."
As a campaigning body set up in 1961, WWF was originally preoccupied with conservation issues, especially those involving endangered species. But in more recent times it has broadened its work to focus on the notion of sustainability, an idea that now underpins all its educational initiatives.
During the debate on the proposed national curriculum, it was at the forefront of the struggle to gain proper status for environmental education. Like other bodies, it was disappointed by the Government's refusal to make it a statutory subject - and to designate it a cross-curricular theme, so making its viability subject to the enthusiasm of individual teachers.
Yet according to Peter Martin, head of WWF Education, the campaigning has had an effect. "It's difficult to evaluate its impact, but we've seen arguments that we've used about education coming back to us in government documents and policy statements. And the strategy published last year, Taking Environmental Education into the 21st Century, is certainly a step forward: we've never had one before."
Faced with a subject-dominated curriculum, WWF Education has made a virtue of necessity, and encouraged subject teachers to consider how the idea of education for sustainability and the exploration of environmental issues can be made relevant to their own specialism.
This has been a relatively straightforward task within subjects like science and geography, where publications such as Ken Webster's Our World: Our Water, Rex Beddis and Cherry Mares's School Links International, and the Atlas of the Environment have been among many titles widely welcomed and used.
More unexpected have been the sorties into areas such as maths, RE and English. Books such as Jill Pirrie's On Common Ground, which links environmental awareness to the creation of poetry, and Antonio's Rainforest, showing life on a rubber plantation through the eyes of an eight-year-old boy, have made a considerable impact.
Music too has been a rich field for innovation, notably with the musical entertainments written for WWF by Peter Rose and Anne Conlon. Covering topics such as rainforests (Yanomamo), displaced people (African Jigsaw), the fate of oceans (Ocean World), and the inequalities of trade (Arabica), they've been widely performed in schools and elsewhere all over the world.
"People need to have strong personal feelings about the issues and the quality of the world in which they live," Mr Martin suggests. "We believe the arts can help them to explore and express those feelings, to develop their own personal relationship with the environment."
WWF Education has also developed a reputation for responding speedily to events on the world stage. Brent Spar, one of a series of Data Bulletins, was put together with the rare collaboration of Greenpeace and Shell, and gives students exposure to both sides of the argument in the controversy over the oilrig's disposal.
"You get a lot of very tired, out-of-date stuff coming up in this field, " says Michael Storm, a former geography inspector now involved with teacher training. WWF's publications are not only of a high-quality, but many of them are produced swiftly and are therefore topical."
A key part of WWF's philosophy is to get young people to think for themselves. "We're not about promoting WWF or a green ethic," Mr Martin says. "We want to give them experiences that will allow them to develop their own responses to issues. So much environmental education only offers them preconceived ideas. "
Another reason for the popularity of the materials seems to be the flexibility they give to teachers. Unlike many textbooks, the WWF publications tend to treat teachers as professionals who know how to plan and execute a lesson, rather than people who require a rigid framework for their teaching.
Recent growth has been in the area of multi-media resources, with the award-winning computer software SATCOM being much admired. Using the idea of a satellite control centre, the programme enables students to survey the globe and zoom in on "hotspots" to identify the environmental issues of the moment.
Colin Harris, another former geography inspector, welcomes the newer IT resources, including the data bulletins covering topical environmental issues. "The variety is tremendous, and the fact that they concentrate on issue-based material is very valuable," he says. "There's a real scarcity of such stuff in this field."
As well as producing this wide range of resources, WWF Education is involved in curriculum development and teacher training through its nationwide Reaching Out programme. This is run by a network of tutors, giving support to teachers who want to integrate environmental education into the mainstream syllabus.
The programme offers residential and other courses to teachers, curriculum co-ordinators and senior managers and aims to help them explore the idea of sustainability, and increase their understanding of environmental issues.
For further details, a free copy of the booklet Curriculum Vitae: The First Fifteen Years (enclose an A4 stamp-addressed envelope), or a catalogue of resources and services, contact WWF Education, Panda House, Weyside Park, Godalming, Surrey GU7 lXR. Tel: O1483 426444