Four o’clock on a Friday afternoon. Time for teachers to switch off. Here, however, 40 eager-beavers are agog with ideas for new projects. Not even the plastic cups of coffee served up in the basement of the National Portrait Gallery (NPG) could dim their enthusiasm. With the help of the gallery’s education staff they have spent the afternoon “decoding” portraits. They are exhilarated by the experience and by its potential to inspire their teaching.

The group of art and history teachers - whose students span all ages from key stage 1 to A-level - from 22 schools in Devon have travelled to the gallery as part of a project designed to exploit the rich potential of portraiture. Some confide that they have always thought of portraits as stuffy and old-fashioned. Now, after engaging with a wide range of images from the famous Holbein cartoon of Henry VIII to contemporary work, they describe the session as eye-opening: “Trailing so many different starting points.”

Armed with their new insights, the Devon teachers will now take students to look at portraits locally, or at the NPG, then decide how the material they find can best be used. In November, the project will culminate in a major exhibition of students’ work in the Royal Albert Memorial Museum, Exeter. There will be more than art and project work on view. The display will also document the practices and processes that have emerged and will act as a basis for the publication of curriculum development papers.

What, you might well ask, have the NPG’s portraits - painted, sculpted, stamped on coins - got to do with today’s children? In an age of spin doctors and gurus, bombarded by serial pictures of the famous, the answer is that nothing could be more relevant. Even if they get little else from looking at portraits, students will gain a vital understanding of the way “image” is constructed. Then they will be in a position to question the images put about by pop stars, politicians, advertisers and other persuaders who want us to see things their way.

This, of course, is just for starters - as the Devon group discovers when the gallery’s education staff John Cooper and Clare Gittins show us “How to look”. Welcoming the teachers’ collaborative approach, they say, “Either for historical evidence or from an aesthetic point of view, the skills of observing, deducing and commenting are absolutely basic. Nowadays children are so used to inter-acting with screen images that the knack of looking at a still image is one they have to learn.”

We begin by looking at slides. First the portrait of a single male figure. What pose did he adopt and why? What is the expression on his face? How is he dressed, what sort of material is it, what quality, what colour? What does it indicate in terms of his social position? Does he dominate the room? What is the significance, possibly symbolic, of the props around him?

Within five minutes of this detective work, without any prior knowledge, we have placed our man. Surprised in the act of writing, and surrounded by books, we identify him as a playwright. Alas, an unhappy one, a Cavalier called Thomas Killigrew, sporting a picture of Charles I, who had been executed the previous year. The liberating thing is the way the education staff use everyday, colloquial language to bring the painting to life. “Look at his kit: he’s brainy but sad. His dog’s devoted to him - just like he is to his king. ”

By the time it comes to our mini-tour of the NPG, responses are coming thick and fast. Grouped, for instance, round one of the most effective propaganda pictures of all time - Elizabeth I bestride a map of England with her head literally in the heavens (see above) - we see how reality was dramatically subverted to signify her dominion.

What about Elizabeth I’s costume? White, like a glorious wedding dress, it implies that the Virgin Queen is married to her country. Behind her, storm clouds dissipate while the sun lightens the foreground.

We guess this alludes to the defeat of the Spanish Armada, but our experts reveal that it also refers to Elizabeth extending her forgiveness to Sir Henry Lee. A one-time favourite, he had been banned from court for taking a mistress - Elizabeth’s courtiers were meant to be in love with her alone and she was jealous of their love affairs. Significantly, her feet on the map are placed on Ditchley, Lee’s Oxfordshire home.

Deconstructing a modern work can be just as illuminating and just as much fun. Take Maggi Hambling’s 1985 portrait of Nobel prizewinner Dorothy Hodgkin, who analysed the structures of penicillin (see below, left). Hodgkin is shown seated at her desk - she may be elderly, but the proliferation of computer printouts shows she is not out of touch. She looks arthritic but, with a touch of the surreal, the painting shows her going about her work with four constantly moving arms. Much evidently remains to be done. A rather obvious symbol, a model of molecular structures, sits on her desk while the tree outside her window links her work with the natural world.

These are just two examples of the way portraits can be decoded. And, as John Cooper insists, “Once you have learned to ask the right questions the skills are transferable.” Other useful questions include: how has the picture space been used? Has the norm been subverted and if so why? (A good example is the Holbein drawing of Henry VIII, where Henry’s dead father is included in order to bolster the idea of dynasty.) What compositional devices are used and why? What about effects of light and shade? Was the portrait intended for private or public consumption?

In a group portrait, what is the relationship of the sitters? Is there any counter-historical evidence showing the portrait image to be flattering or downright false? From an artistic point of view, the 20th century has valued originality, whereas the Tudors and Stuarts used copies of portraits to disseminate their chosen images. Was their publicity any different from that now used by the Spice Girls?

When it comes to follow-up work for their students, the Devon teachers are buzzing with suggestions: self-portraits of students, family histories involving photography, studies of local celebrities with appropriate accessories and history projects with the Tudors, Stuarts and Victorians.

One interesting idea is to tap into the NPG’s alluring picture of Sir Henry Unton. Recording his whole life from cradle to grave in painted snapshots, it provides a rich variety of themes. It can also be usefully linked to contemporary work like David Hockney’s multiple perspective paintings. Chris Wightman suggests visualising portraits like that of Elizabeth I in geometric terms, then reinterpreting them in the manner of early abstract painters like Fernand Leger or Kasimir Malevich. John Cooper instances a history project where students made clay tiles of the Tudors. The possibilities are endless.

HOW DEVON TEACHERS CAME TO LONDON

The project was organised by Devon County Advisers Chris Wightman (art) and Chris Taylor (history). They had obviously put a good deal of work into setting up the scheme, providing background support and, when necessary, spoon-feeding. For a contribution of Pounds 200 the schools received:

* An introductory briefing meeting;

* An extensive teacher’s resource pack with background notes and follow-up ideas;

* The coach visit to the National Portrait Gallery (NPG) for two teachers per school;

* A three-hour session with education staff at the NPG;

* A one-day programme with NPG education staff at two local portrait venues: Montacute, the National Trust House near Yeovil which has a permanent NPG collection, and at the NPG’s touring exhibition, The Room in View, at Exeter;

* An evening workshop with the advisers to discuss evolving ideas; * Materials, including film for documentation of projects and for the final presentation of work;

* The exhibition in the Royal Albert Memorial Museum, Exeter, next November.

ROOMS WITH A VIEW

* Details of the Devon initiative: Chris Taylor 01392 382053 or Chris Wightman 01392 384831;

* The National Portrait Gallery (NPG) education department welcomes visits from groups studying the Tudors, Stuarts and Victorians at key stage 2, and GCSE groups following the schools history topic on the English Civil War. For sixth-formers, skills-based day courses are run on portraits, historical painting and caricature as evidence. To book a school visit call Sarah Hartley on 0171 306 0055, ext 212

* The Room in View, a NPG touring exhibition is at the Royal and Albert Memorial Museum Exeter until June 14. Then at York City Art Gallery from December to January 1998.

* Maggi Hambling’s Oscar Wilde sculpture is at the NPG until August 3.

* A Matter of Life and Death, new sculpture by Maggi Hambling, is at the Yorkshire Sculpture Park from June 16 to August 10.

* Recommended books: Susan Morris, A Teacher’s Guide to Using Portraits, English Heritage 1989; James Hall, A Dictionary of Signs and Symbols in Art, John Murray 1974; Jude Welton, Eyewitness Art: Looking at Paintings, Dorling Kindersley 1993; Sir Henry Unton: An Elizabethan Gentleman, with four slides, only available from NPG bookshop, 0171 306 0055 ext 223.