You know the plot because you have seen it umpteen times: inspirational teacher arrives at inner-city school to face a challenging class, but eventually manages to gain their respect and admiration. Cue credits. The tale of the hero teacher has been a solid sub-genre of the school movie since The Blackboard Jungle in 1955, its story re-used so many times that it has inspired parodies.

But The Class, which opens in UK cinemas next week and is nominated for an Oscar this Sunday, does not follow the standard plot. Indeed, it may lay claim to being the most realistic fiction film about teaching yet.

Apart from a few scenes in the staffroom and playground, nearly the whole film is shot in the classroom. It captures the perpetual struggle of Francois, the teacher, as he tries to keep his class of 14-year-olds on task. Sometimes he uses the pupils’ interruptions and tangents to start a new debate or steer them back on to the topic. When a pupil starts moaning about how hamburgers “stink”, he tries to get him to examine the verb.

But Francois’ lessons do not go smoothly and are full of stops and starts as he tries to clamp down on low-level misbehaviour, bat off personal questions and stop rows.

Star Francois Begaudeau is convincing as a teacher because he was one. The script is based on his semi-autobiographical novel Entre Les Murs (literally, between the walls), inspired by a year he spent teaching at a tough multicultural school in Paris.

It attracted the interest of Laurent Cantet, the 48-year-old French director, whose parents were teachers. “Schools are one of those places where each one of us has formed an impression of how to look at the world,” he explains. “The school is one of the most beautiful institutions, but also the most terrifying. People talk a lot about school, but actually don’t really know what goes on inside. But if you look at a live lesson, you avoid the stereotypes, you avoid the ideological positions and you see the real people.”

Mr Cantet read the book then devised a structure for the film, which follows a year in the school and focuses on one misbehaving pupil, Souleymane, who is at risk of exclusion. He held weekly workshops with pupils, videoing their improvised lessons. From these he picked the teenagers who would play key characters.

The scenes in the film were also semi-improvised, and shot using just three cameras in the actual middle school, Francoise Dolto, where Mr Begaudeau taught.

The teachers were all real staff at the school. “From the start, the teachers were very interested in the experience,” says Mr Cantet.

“The only difference between them and the pupils was that they had read the script. The work we did together was more reflective, so we talked together more - more than improvising.”

Mr Cantet is at pains to point out that the teachers played fictionalised versions of themselves, noting that one, Bernard - who in the film opposes some of Francois’ more liberal approaches to teaching - is more like Francois in real life.

Indeed, Francois’ methods have divided teachers in France, where the film provoked debate about teaching practices when it was released last year. Some regarded his lessons as too laid back, while others were surprised by his strictness and loss of temper.

“Because it is fiction, there is a choice about what we show, and the moments that I felt like showing were moments of discussion and of confrontation - often moments when the lesson slips away in another direction towards questions of why they are there,” Mr Cantet says.

When the book and the film came out in France, many teachers said that the characters seemed to talk more than teach.

“There have been some ideological reactions to his pedagogy and the fact he lets himself get taken over by personal feelings,” says Mr Cantet. “I think those teachers would have liked it if we had created a character of a teacher who was much more emblematic.” They did not recognise themselves in that sort of teacher, he added.

Those teachers would have hated the 2007 film Half Nelson, a film about a teacher heroin addict. Mr Cantet laughs: “At the same time, they would love Dead Poets Society - this guy who always has a good sentence to say, who is a supreme guide.

“Through my parents’ friends and colleagues, I saw teachers who lived through their job in a very committed way,” says Mr Cantet. “It was not just about transmitting knowledge - because that, to some extent, is fairly easy - it was people who realised it was important to give meaning to what you do at school. But I wanted to show a bit of the back stage and the human side of teachers - that they have moments when they think of something else as well.”

These staffroom scenes were, Mr Cantet says, a real eye-opener for some of the teenagers who have seen the film: “One was amazed to see teachers talking among themselves, and to see them talking about pupils.”

As well as being a surprise hit with French teenagers, The Class was the first French film in 21 years to win a Palme d’Or at the Cannes Film Festival. Mr Cantet and Mr Begaudeau will learn on Sunday whether it has won the Oscar for best foreign film.

Even Chris Woodhead, former chief inspector of schools, is full of praise, recommending the film to anyone “who wants to know the truth about teaching in an inner-city school”. He says it “raises disturbing questions about the lunacy of secondary education as it now is in the developed world”.

The film does indeed show depressingly familiar poor behaviour. One boy tries to wind Francois up by asking if he “likes men”. Then, when two pupils mess around at a school meeting, Francois gets in trouble for making an unwise comment.

However, the film also appears sympathetic towards the pupils.

Mr Cantet’s previous films Time Out and Human Resources explore workplace power and he is clear about where it is in schools. “We mustn’t lie to ourselves - the power is with the institution and the teachers,” he says. “And maybe because they are very aware of it, the pupils rebel against this power.”

He admires Francois’ liberal approach: “Francois tries to create a very egalitarian rapport with his pupils in their dialogues, and if he succeeds in teaching something it does not matter who is talking.

“It may be a utopia - this idea that ‘I can’t possibly teach from above’ - but Francois wants to be on that equal footing when he is teaching.”

But, unlike films of the Dangerous Minds mould, Francois’ lessons do not always come good. In one powerful scene, a tearful pupil, Henriette, says she has learnt nothing all year.

“We expel some childrem, and we also exclude pupils like Henriette, who doesn’t understand what she’s doing,” Mr Cantet explains. “Academic failure is much more widespread than discipline issues.”

He is concerned about the way schools sort pupils into groups, demonstrated in a staffroom where a teacher goes through a colleague’s register for a new class, pointing at names and saying: “Nice ... not nice ... nice ...”

But, although the film touches on contentious topics such as immigration and nationality, Mr Cantet does not want it to be regarded as a polemic.

“It’s not a commentary film about education,” he says. “The film is just to say what happened between those 25 people, what is at stake for them and what the school can bring. I show the world by asking questions rather than giving answers.

“I’m sure it will be easier for a British teacher to watch it than a French one because they will have a distance - the mirror will not be quite as close for them.”

WATCH IT FOR FREE

Special free screenings of The Class are being held for teachers and schools at cinemas across Britain on Monday, ahead of its nationwide release next Friday (February 27). Tickets are available on a first-come, first-served basis for the Film Education events. The certificate is 15 and suitable for AS or A-level students studying French, film studies, citizenship, English and media.

The screenings will be held at:

- Bristol: Watershed

- Cambridge: Cambridge Arts Picturehouse

- Cardiff: Chapter Arts Centre

- Edinburgh: Cameo

- Glasgow: Glasgow Film Theatre

- London: Curzon Mayfair

- Liverpool: Picturehouse

- Norwich: Cinema City

- Nottingham: Nottingham Broadway

- Sheffield: Showroom

For details, visit: www.filmeducation.org

For more about the film: www.artificial-eye.comtheclass.