Today’s children know all about evil: they confront it routinely in fantasy books, monster movies, computer games and action videos. The formidable challenge in teaching them about history’s most devastating programme of systematic genocide, accomplished within the memory of their grandparents, is to distinguish it from the formulaic horrors to which they have become effectively inured. How do you bring home the reality of something so inconceivably terrible?

That was the task facing the creators of the Holocaust exhibition at London’s Imperial War Museum, to be opened by the Queen next Monday. In particular, it has been a constant concern of Paul Salmons, the museum’s Holocaust education co-ordinator, since he joined the project 18 months ago from Notre Dame senior school at Lingfield, Surrey, where he had been head of history.

“A major factor throughout the whole design is how to tell such an awful, tragic story in a way that’s acceptable to students,” he says. That is why survivors’ personal reminiscences run as a consistent thread through the exhibition. Students will first meet these witnesses in the half-hour preliminary video sent to schools that book group visits, then in audio-visual clips and other material in the exhibition itself.

One is Roman Halter, born to a Jewish family in a small town in Poland. He tells how he saw his former best friend, a German Pole, take part in a murderous attack on fellow Jews; how he survived the hardship of the Nazi-imposed ghetto and, later in the war, was sent to Auschwitz and escaped from a death march. Another is Beata Green, whose father, a Jewish lawyer, was beaten up and paraded through the streets of Munich by the Nazis soon after they gained power. She escaped just before the war on the Kindertransport, the special trains that took Jewish children to Britain.

“They will get to know these people as they go through,” says Mr Salmons. “Otherwise you just get faceless victims and anonymous bodies. The witnesses we talk to now were children at the time. It’s a strength from the education point of view that, although they’re elderly people, the way they talk about those experiences is as if it’s still through the child’s eyes. Their testimony is very accessible because of that.”

The Holocaust exhibition represents a significant broadening of the museum’s coverage of the Second World War, in its public displays and educational provision. In part this is a response to the inclusion of the Holocaust in the national curriculum, and in part to the explosion of interest in the 1990s, coinciding with the 50th anniversary of the war.

“In this country the general perspective on the war is based on parents’ and grandparents’ experiences - the home front, the Battle of Britain, Dunkirk - and we’ve always reflected that here,” says Mr Salmons. “The Holocaust has been seen mainly through the image of liberation of the death camps. This exhibition will rapidly change people’s ideas.”

Class visits will begin in the autumn term and schools will receive circulars about them in the next few weeks. The museum can cater every day for eight groups of about 30 children from Year 9 upwards: those under 14 will not be accepted in the groups and are discouraged from visiting the exhibition at all.

When they book, teachers will be asked which aspects of the Holocaust they want to focus on, and how far the class has reached in its study of the subject. For most classes it will be part of the history curriculum, but Mr Salmons sresses that it can also be focused towards English, citizenship, music and religious studies. (Where was God in the Holocaust? Why didn’t more people help the victims? What was the role of the Christian churches?) Each group will be given a 15-minute orientation session from one of a dozen newly recruited educators, tailored to the priorities specified by the teacher. Pupils will then be given individual educational audio guides that will help them pick their way through the exhibition. There is one version for Year 9GCSE candidates and another for students with moderate learning difficulties. A guide for pupils with visual impairments is in preparation.

The exhibition is on two levels. The top floor covers the period 1918 to 1939, tracing the rise of the Nazis and the gradual imposition of laws that branded Jews as second-class citizens. It shows how attacks by stormtroopers on Jews and their homes and shops were encouraged by the regime. Alongside these chilling displays are home movies, family snapshots and modest domestic items that illustrate the everyday lives of Jewish people - images of a vibrant culture and society for which pupils will have been primed by the pre-visit video. “It’s important that children should have a grounding in what the people were really like as individuals,” says Mr Salmon.

Jews and other persecuted groups, such as homosexuals, gypsies and the disabled, were slow to recognise the real peril they were in. And when, on the eve of the outbreak of war, they eventually tried to escape, it was difficult to find a country willing to accept them.

The lower level, covering the war years, is inevitably dominated by the death camps. The images of emaciated survivors and of bodies piled into mass graves are no less harrowing for being dreadfully familiar. One gallery features a large model of part of Auschwitz, recreated from contemporary photographs, as a train arrives and unloads thousands of Hungarian Jews. Alongside it is one of the carts used to transport the bodies. On the positive side are stories of how the victims sought to resist their captors, physically and spiritually - belying the common image of abject people passively accepting their fate.

Retribution, though necessarily inadequate, is celebrated in a section on the Nuremberg trials and the execution of many perpetrators of atrocities. In the final gallery visitors are invited to sit and reflect on the lessons of the Holocaust, in front of more videos of survivors. School groups will go back to meet the person who conducted their initial orientation for a 25-minute discussion on what they have seen.

This month Mr Salmons is organising three seminars for teachers who intend to bring classes along. “It’s important that they’re able to prepare their students properly,” he believes. The most difficult issue for discussion will be any link between the Holocaust and the racial hatred and intolerance that flourish today in many parts of the world. While children can watch daily accounts of such events on television news, it is difficult to reassure them that nothing as evil as the Holocaust can ever happen again.

The Imperial War Museum, Lambeth Road, London SE1 6HZ, is open daily from10 am- 6pm. For enquiries on class visits and the teachers’ seminars contact the booking office on 020 7416 5313. An interdisciplinary teacher’s resource pack and student’s book will be available later this month.Michael Leapman’s Witnesses to War, an account of children’s experiences under the Nazis that won the TES Senior Book Award in 1999, is to be reissued as a Puffin paperback