Imagine a school where pupils as young as 12 are recruited to spy on their classmates. Where the teachers aid and abet this child espionage. Where student essays are scrutinised in the hunt for suitable spy material. Where the recruitment takes place at the very heart of the school - in the headteacher’s study. Now imagine this is not one isolated school, but every school in the land, until an army of 10,000 young spies has been assembled.

It couldn’t happen here? Well hopefully not. But it did happen, quite recently and not that far away. Thousands of young people were recruited as spies of the dreaded Stasi secret police in East Germany before the fall of the Berlin Wall in November 1989. And thousands - both betrayers and betrayed - are still suffering the consequences.

Antje was one of the betrayers. Today she is a 29-year-old woman beset by depression, guilt and self-loathing. It began back in 1986 when she was a confused 17-year-old schoolgirl. “It was out of the blue,” she says, recalling the day that marred her life. “I was asked to come to the principal’s office. There I met a man in his mid-20s. All I knew about him was he was from the Stasi. He asked if I was prepared to help the Stasi, and because I was supposed to meet a friend and was impatient to get away, I agreed.” The friend she had to meet was one of few - Antje was not popular at her East German grammar school. She admits herself that she was not attractive as a teenager, did not stand out in a crowd. And that was what made her ideal fodder for the Stasi. East German psychologist Klaus Behnke explains: “The Stasi sought out the insecure, the vulnerable and manipulated them. They were mostly misfits or weak. They were given a sense of belonging. Young people were taught to mistrust everyone except their Stasi controller who they had to trust completely.” So a plain girl with no boyfriend would be introduced to a young Stasi officer and told she was beautiful. Psychologically disturbed youngsters were made dependent on their controller’s affection and attention. And there were others in trouble, particularly petty juvenile criminals, who were able to “buy” their way out of punishment by becoming informers.

Three months after the first meeting with her “controller”, Antje became one of the Stasi’s 10,000 informers under the age of 18 when East Germany’s communist system collapsed. Her job was to infiltrate church and ecology youth groups and report on the members.

But if the Stasi aimed to gain control of her mind, they failed. “I began to understand the groups’ motives myself and began to identify with those I reported on. It was difficult to stay detached. I tried to stick to describing the aims of the group rather than the individuals I liked. But it was hard. I had great difficulty trying to decide what to write.” She met her controller regularly, sometimes in her own home, but received little feedback on her work and never questioned what was required of her.

Anger still runs high in Germany today over the role of the Stasi’s known 173,000 informers. But unlike their adult counterparts, child informants -some 6 per cent of the total - are seen as victims of their own youth and ignorance in a system which demanded conformity and obedience. As “victims” their names are still blacked out in Stasi files to protect them from retribution. The first teenagers were recruited in the late Seventies and by the Eighties, the youth network had been systematically built up.

Some youngsters received payment but these were not large sums, says Edda Ahrberg, who is responsible for the former Stasi archives in the state of Saxony Anhalt. “More important for the informers was the recognition; the feeling they were important and needed. Most of them were low on self-esteem.”

The age of recruits was dropping rapidly and by 1989 it was not uncommon for 12-year-olds to be informers. They were carefully selected by systematically monitoring school essays. Most teachers, whether or not they were Stasi informers, were involved. Many youngsters resisted. Indeed records suggest that four out of five refused. But some felt they could not.

“It was clear to me I could not say no,” says Robert, recruited at 17 in 1983. “To say no was like saying ‘Of course, I’m an enemy of the state’.” Others say that, because the first approach often took place in the headteacher’s office, they thought writing reports for the Stasi was part of what was expected at school.

For Antje the strain grew ever more intense as she began to identify more and more with those she was betraying. “The more I got to know the group I was informing on, the more pressure I felt. I feared losing the friends. I feared there would be some danger to myself and consequences for my family. Yet I felt controlled. I was in a bad state mentally. Very depressed.” She was gripped by fear in 1989 when East Germans were allowed to consult their own Stasi files. Public anger against Stasi informants was raging. “I felt like a third-class person,” she says. “I barely went out.”

Many young informers have grown into deeply disturbed adults, unable to take responsibility for their own lives, always used to following orders and isolated from their peers, many of whom cross the street now when they see them. Paranoia and depression are common. “They are so used to being controlled,” says Behnke, who counsels former child informers under a programme set up by the Berlin authorities.

Antje decided the only way to conquer her fears was to face them. “After the wall came down I rang the friends that I informed on and told them myself. There was silence on the phone at first and then they agreed to see me. We spoke of ethics. What are the limits? When do you step back? In the society we were in, we were taught not to question.”

Why did the Stasi go to such lengths? Behnke, whose research has just been published in Germany under the title Stasi auf dem Schulhof (Stasi in the Schoolyard), believes it was part of a highly-organised plan to quell any kind of “rebellious behaviour”. “Decadent” youngsters, including hippies, punks and ecology groups, had to be stamped out before they became adult dissidents and a threat to the monolithic state. “They could not cope with these new ways of thinking. They infiltrated them with young informers in order to understand the ‘threat’ and to destroy it,” he says. How much harm did the informers do?

Young people convinced they missed out on a university place for political reasons are only now trying to seek compensation, but they are unable to prove specifically who informed on them because of the policy under which the names of child informers are blacked out in the Stasi files. “Any compensation would only be symbolic,” says Behnke. “A court cannot give back opportunities missed in youth.”

Antje believes she only contributed to a file of information on a group of people who were already under suspicion because of their links to the church and ecological organisations. Teachers may have provided more damning information. But there is no denying that young people suffered at the hands of the Stalinist state. Restrictions, threats, blackmail and pressure led at the end of the Seventies to a wave of suicides among 14 to 17-year-olds in the eastern new towns of Hoyerswerda and Goerlitz, where a number of church and punk groups were active. Suicides fell to less than half the Seventies rate as soon as the Berlin Wall came down.

As for the former child informers, some now attend Behnke’s practice. Many are “really ill”, he says, with psychosomatic symptoms, addictions and attempted suicides. “Some of them are unable to function in society and face years of psychiatric treatment.” Antje was in therapy for a year and is still prone to depression. Unusually, she is still in contact with the group she informed on. “They became my friends,” she says. She still feels the overwhelming guilt of having betrayed them.

Many teachers who assisted the Stasi are still working in the East. Often there is little proof of their role, but testimony from former child recruits points time and again to the teacher’s role in steering them into it. Birgit Siegmann, a teacher in the eastern town of Halle, remembers: “A teacher from Leipzig wrote to the Stasi to ask whether she should make imprints of the pupils’ housekeys during break-time when the children were all outside. She then did so. She was not a Stasi informer. She merely had an ingrained understanding of the Stasi’s growing need for information.”

According to the Berlin agency in charge of former Stasi records, some 15,000 teachers have been investigated to date and almost 5 per cent of them were found to have had proven contact with the Stasi. But only a quarter of these have lost their jobs. The majority continue to teach.

In the state of Saxony Anhalt, archivist Edda Ahrberg is not alarmed when she notes that three-quarters of investigated teachers still teach. “Those who actively collaborated were a very small circle. Among the criteria for disciplining teachers for their past activities is the principle that they must have been responsible for what they did.”

For headteachers, that responsibility is more clear cut. Informing on teachers and pupils was part of their job. They were duty bound by means of a written agreement to provide information to the Stasi. “The extent to which the principals acquired information on the private lives of teaching staff and pupils cannot be gleaned from the Stasi files. It is hugely underestimated,” says Ahrberg. “The extent to which principals ruined young lives is incalculable.”