"Did you know that your grandparents killed my grandparents?” The young German filmmaker Elena Horn has never forgotten these words, said to her during her first ever encounter with a Jewish person, on a night out in London, aged 21. In that brief interaction, it felt to her like the tall, athletic American had “taken a baseball bat, and slammed it into my face.”

For a few seconds, she came to represent “all the crimes committed by the Germans against the Jewish people,” she says in a voice-over at the start of her thought-provoking documentary The Lesson, “and I’m drowning in the guilt.”

This painful experience made an indelible impression on Horn, who tells me from Germany that she couldn’t stop thinking about it for the next three years. The Lesson — in which she returns to her home town to examine how teenagers are taught about the Holocaust — arose from her wondering why she had reacted so emotionally to something said to her by a stranger whom she never saw again.

“I thought I must have learnt this somewhere. Somehow it must have entered my system. And because it definitely didn’t come from my parents, I thought it must have come from school.”

Horn had an idyllic childhood growing up on a farm in an area little changed since before World War Two. She describes it as being like the beginning of a Grimm brothers’ fairy tale. The war was talked about rarely, and today she doesn’t have “any firsthand story I can tell or anything, because I never met any of my grandfathers. So my connection to the war is more through my grandmother. She was in Silesia and fleeing the Red Army, but she was only, like, six.”

At age 14, she began, like every German schoolchild, to learn about the Holocaust, and her world suddenly darkened.

At home, a state of blissful ignorance had been cultivated, which she found strange given that she could go to watch Borussia Dortmund play nearby, a football team notorious for having neo-Nazis among its supporters, and hear racist and antisemitic chants in the stands. (In October 2020, the club officially adopted the IHRA working definition of antisemitism as part of a strategy to counter the longstanding problem.)

“Always there’s this idea about trying to protect this holy childhood. Like my father told me I’m only able to read certain books when I’m 18.”

Even now, says Horn, “I find it very upsetting that it is still very difficult to get information from your relatives. It [just] comes in drops, or tiny little details.”

The classroom, then, is where the first real education about the Holocaust begins for most German children, who frequently start with only a vague grasp of their country’s recent past. According to a poll quoted in The Lesson, 40 per cent of German children don’t know what Auschwitz is. Did Horn resent being rudely woken from her pastoral idyll by school?

“It’s the moment when you transition from your nation being a football team, more or less, to having a little more historic understanding of your nation — and it’s not a particularly positive one in Germany. So yes, I was angry.”

At the same time, she told herself that she would have been a hero and not like the millions of Germans who let the Holocaust happen. “But it’s very naïve,” she concedes. “It’s very easy to say that when you’re 14 and no one’s putting a gun to your head.”

Not that a gun was always necessary. In The Lesson, a grandmother who grew up on a housing estate named after Rudolf Hoss, ruefully tells her granddaughter that being given comforts such as a laundry room and heating could be enough to make people look the other way. She hoped that the new generation wouldn’t make the same mistakes.

This gets to the heart of the documentary. Is Holocaust education in Germany fit for purpose? The rise of antisemitism and resurgence of the Far Right in her country made Horn feel that something was going wrong. She had grown up in a “culture of guilt”. Was it still the same today?

She returned to her old high school in Frondenberg, a town in North Rhine-Westphalia, thinking she could “witness how it grows over time”. But in the years Horn filmed, from 2014 to 2019, she “didn’t find the culture of guilt. I could see it in the teachers, an awareness that there is a guilt of the nation that remains, but I didn’t see it in the kids.”

In the 1930s, the Mitlaufer, or bystanders enabled Nazism. Worryingly, Horn found that just the idea of demonstrating against the neo-Nazis in Dortmund was out of the question for some students, who were cowed by the possibility of violence. One even said her family so enjoyed their life, they would probably accept suppression.

“I remember one of the teachers re-living his disappointment over this,” says Horn. “He was questioning if we can talk about ‘successful teaching’ in this case.”

While the school welcomed Horn, keen to show the experience of Holocaust education through the eyes of pupils, some teachers wouldn’t let her film in their classrooms. “Their explanation was that there are students that clearly hold extreme right-wing views. They were worried that it might stick to these students forever if I film them now, even if they change their mind in the future.”

She did film a girl, though, who is torn between what she is being taught in school and told at football training, where her teammates and coach claim her teachers are lying. At home, her grandfather keeps his Nazi medals in a kitchen drawer and, although it isn’t in the documentary, celebrates Hitler’s birthday. “He, of course, didn’t want to film with us,” says Horn.

I ask if German children are influenced by Holocaust denial on social media. Horn’s impression is that the issue is less one of denial in Germany than a belief that the Holocaust was “exaggerated by the allied forces in order to give the entire guilt for WW2 to the Germans.” Often it is treated as a closed chapter, almost ancient history. “You know, 8th of May [Liberation Day], all gone. Of course, it’s not like that. But that’s why it starts to feel like learning about the Romans or the Middle Ages,” she says.

Horn recalls that when she was at school, people were already saying, “‘There are no survivors any more’ and ‘all the perpetrators are dead’, subsequently we don’t need to engage with this topic to such an extent. I find this way of thinking very harmful.”

As she filmed, she discovered a failure to make the lessons of the Holocaust, and the world it grew out of, feel relevant to students. “Even though we have things like the [2019] attack in Halle, we have the National Socialist Underground, we have a huge number of people with National Socialist ideology in the police, in the army, in the secret service, this is nothing you touch on in history class.”

She makes a comparison between Germans who say nothing when their Afghan neighbours of several years are refused residency and get pulled out of their flats by the police and sent home to a situation they might not survive, and the bystanders who let the small improvements in their lives trump any desire to protest when Jewish neighbours were dragged from their homes. “As humankind, I think we’re still so primitive that we have to make a constant struggle to fight for human rights,” she says. “And because there’s no natural way of doing this, we have to do it collectively.”

Holocaust education is “still very perpetrator focused.” In one class, Horn filmed children immersing themselves in the mindset of the designers of the Sachsenhausen concentration camp, a model of German efficiency. Queasily, the Jewish victims are reduced to an abstraction, “like a ghost people,” agrees Horn, “that should be there but are not.”

We don’t hear what the children think of Jews in the documentary. It seemed to the director, though, that most of their preconceptions came from history classes, and she was troubled by the way that attempts to combat antisemitism began with exploring explicit antisemitic stereotypes. “It’s a contradiction that is hard to digest,” she says. “By trying to avoid antisemitic ideas in our society, we are also teaching these negative ideas in the first place.” Most shocking was the way that children referred to Jews as Auslander — foreigners — and how “the idea of a German Jew seemed completely alien. To many of them, Jews are still people who come from far away and migrated to Germany. They use the same terminology as they would use to describe a Syrian migrant who came here in 2016.”

Children are malleable, and fascinating footage found by Horn in a local archive shows how a Nazi mindset was inculcated in them after Hitler became chancellor. It is chilling, but also offers hope by showing that what happened wasn’t an accident. The Far Right is on the march once again, but “Never Again” need not just be hollow rhetoric.

“I think it is very important not to think that there was no alternative to the road that Germany took in ’33,” says Horn. “It is so lazy of people to believe that there was just this general movement and trend which was unstoppable to go to fascism at the time. It was not like that then, and it is not today. So, I think both political and civil society have the cards in their hands. It’s just the inactivity which is the absolute poison for us now.”

The Lesson screens as part of the Human Rights Film Festival, March 18-26. www.barbican.org.uk/whats-on/2021/event/the-lesson-12