People assign a lot of terms to the films of the French director Laurent Cantet, terms that typically point to the social themes of his stories or the naturalism of his methods. Mr. Cantet, who frequently wraps his fictional tales in documentary threads, has spent the last decade focusing chiefly on the ways in which class differences tug at the soul of a society.

In 1999, Mr. Cantet made “Human Resources,” which parlayed a family scuffle into a labor dispute, with a white-collar son finding himself pitted against his blue-collar father. In 2001, with “Time Out,” Mr. Cantet told the story of a man who neglects to inform his family that he has lost his job and slips down a spiral of fear, shame, and self-disgust. Four years later, Mr. Cantet’s “Heading South” examined the rift separating First World tourists and Third World sex workers, as white women of privilege traveled to Haiti and paid handsome men to be their sexual companions.

Mr. Cantet’s films are piercing but also empathetic, reflective of a director intent on making a point but also open to the notion of loving his flawed characters. His latest film, “The Class,” is a pressure cooker of drama, based in a Paris public school and set to a high boil. As the film spans the course of a full term, viewers are privy to a series of tense exchanges between students and a grammar teacher — arguments that show the larger ethnic, racial, and class tensions currently embroiling French society.

As social drama, “The Class” is a subtle and immersive experience, a film described as a “cumulative” drama by Kent Jones of the Film Society of Lincoln Center. On Friday, some four months after it unexpectedly claimed the top prize at the Cannes Film Festival, “The Class” will officially ring in the 46th annual New York Film Festival, singled out as this year’s opening-night selection.

One can easily sense why “The Class” has become a hit on the film-festival circuit. It is a challenging film, but not overtly obtuse. It is engaging and emotional, all without being syrupy. Unlike other message movies, “The Class” is defiant in its refusal to telegraph its message from the first scene. During a recent visit to New York, Mr. Cantet explained that he wanted to use the classroom as a microcosm for a nation.

“I see this like I saw ‘Human Resources’ and maybe ‘Time Out,'” he said, “as a film that takes the time to look at the small world and see miracles — to see what a single story can say about the larger society all around us. I like films that make people think, and I hope this one helps people to think about school and democracy and what is culture, and all the problems associated with that.”

A few years ago, Mr. Cantet said, he had already decided to make his next film about a racially diverse, inner-city school when he became aware of a book by François Bégaudeau, a longtime teacher who sat down and wrote about his experiences. “Entre les Murs” was an autobiographical novel that captured both the inspiring victories and discouraging failures that punctuate life in the classroom. Once recruited to make a big-screen adaptation of the book, Mr. Bégaudeau encouraged Mr. Cantet to create a “realistic experience” that would add a degree of reality and spontaneity to such standard fictional classroom dramas as “Dangerous Minds” and “School of Rock.”

“François proposed a character of the teacher, this teacher who faces his class in a very powerful way, and we wrote a script together that was not very precise on the dialogue, but sketched out the way people would react based on the experiences he captured in the book,” Mr. Cantet said. “But much of the film came out of our workshops in Paris, where we found parts of the improvisation that we liked, where we really found the characters of the students, and were able to create a rough script from those moments.”

After casting Mr. Bégaudeau himself as the film’s central character, Mr. Cantet organized workshops over the span of several months, bringing the teacher and sometime journalist together with other teachers and students from a junior high school in the 20th Arrondissement of Paris. The goal was to improvise and hone the chemistry, conversations, and confrontations of a real-life classroom.

It was during these workshops that Mr. Cantet found the issues and discussions that would come to populate his true-to-life film. Witnessing the ways in which the teacher-student relationship often devolved to a feisty tug-of-war helped the director shape his script into something more relevant and realistic. But the improvised classes led the director to the two-dozen students he would eventually employ in the final production of “The Class.” When principal photography began on the film’s one and only set, Mr. Bégaudeau and his fictional students had established a believable chemistry and rapport.

The result is a compelling, multilayered case study of the personalities, tensions, and everyday dramas that teachers address on a daily basis in any urban school environment. As the opening-night film for a festival in a city with more than 1 million public school students, “The Class” will surely resonate with every public school teacher — not to mention every filmmaker trying to replicate Mr. Cantet’s success in giving a fictional movie the weight of a nonfiction story.

“It takes place in a school, but the real question we’re asking here is much bigger. What is our identity? What is our French identity?” Mr. Cantet said. “I thought it was important to show the reality of a French school — the kind of school that exists in some parts of Paris. Understanding diversity is something that’s very important, and it is something that some people are not entirely comfortable discussing right now. When I was a kid, I was in a school with children who all looked like me. But now here’s a much different classroom, and I wanted to show how rich this can be, to mix all these cultures together, learning how to live and work together. It’s a space of democracy.”

ssnyder@nysun.com