Slight of stature and soft of voice, Cristian Mungiu is an unlikely leader of a cinematic revolution. But ever since his second film, the harrowing abortion drama 4 Months, 3 Weeks and 2 Days, won the Palme d’Or at Cannes film festival in 2007, Mungiu has become the best-known director, and de facto leader, of a group of film-makers who emerged a decade ago from post-communist eastern Europe – and most particularly, the new wave that exploded from Romania, the country that experienced the toughest transition from Soviet domination in the late 1980s.

Now, almost 30 years after the revolution that led to 1,100 deaths and ended with the overthrow of Nicolae Ceaușescu, Mungiu has a new film in cinemas, only his third since that breakthrough a decade ago. Called Bacalaureat, or Graduation, it’s a knotty fable, thick with disillusion and shabby compromise: a surgeon in Romania’s second city, Cluj, is desperate to get his daughter to university in Britain, but just before she takes her crucial exams, she is attacked and sexually assaulted. Fearful that, despite her hitherto excellent academic record, the trauma will mean she won’t get the required grades, he resorts to back-slapping, payoffs and favours to try to secure the right result.

Watch the trailer for Graduation

Graduation is, rather obviously, a portrait of a society still befuddled by its transition from authoritarianism, blinking in the harsh light of crony capitalism. But Mungiu bridles a little at the suggestion that the film is a comment on the difficulties of adjusting to a society without communism – “When you make a film from a communist country, people always relate it to communism, because they don’t know anything else about these countries” – and says that it’s gone down well in places that never belonged to the Warsaw Pact. “People relate to it much more than you would imagine in countries where there was no communism. In Italy and Greece, it felt like it could happen there as well – wherever people feel they don’t progress or advance in society based on their own merit.”

One striking aspect of Graduation is its central character’s touching certainty in the benefits of a British university education. Here, at least, Mungiu is prepared to acknowledge the seepage of the post-totalitarian experience. Under communism, he says, “people did not have information” about the west and “just fantasised about it”; it was not just a question of money, but of “a place where everything goes better: people are more honest, rules and regulations are respected”.

“For us, if you live 50 years in a country where the authorities were so corrupt, so unfair to people, all this moral compromise you see today is a result of that period. Maybe we had too high hopes, but we were very naive: we thought after the fall of communism that not only that freedom will come, but wealth will come as well. It never happened like this.”

Mungiu’s Palme d’Or-winning abortion drama 4 Months, 3 Weeks and 2 Days. Photograph: Sportsphoto/Allstar/Saga Film

Mungiu itemises the process of disillusion: he was in his early 20s when the revolution happened, and most of his generation, “decided to just leave: you have one life and you want to be happy tomorrow”. As a new generation grows up, however, “it’s much more complicated. For people now it’s very clear: it’s hopeless to think you can change things in Romania for your own lifetime, but maybe it’s worth it for the children.”

In fact, he says, Graduation developed out of his own reflections on parenthood, and how to gauge the best way forward for his own offspring. He mentions a trip with his kids to a playpark on the outskirts of Bucharest. “All of a sudden, the polite stuff I told them to do at home didn’t work. It was about who was the toughest. I began to think: maybe I’m not preparing them properly for society. Will they just be losers if I keep telling them to be fair, and respect the rules, if no one else respects them?”

He talks about migration as “an individual solution”, in some ways easier than sticking around and trying to effect social change, the “collective solution”. “When I was at school,” he says, “we were called the ‘generation of sacrifice’. But our parents were called the ‘generation of sacrifice’, too. Now I hear our children being called the same. Frankly, it is a sign that things are not healthy.”

Cinematically, Mungiu has responded to this bleak assessment by developing a style that reflects the powerlessness and fear at work just beneath the surface: he deals in characters who are trapped and bewildered, grasping at straws but swamped by unforeseen consequences. It’s also possible to chronicle – sort of – Romania’s evolution through his three principal feature films. The metaphor of an illegal abortion defined the new society’s birthing agonies in 4 Months, and gruesomely illustrated the stillborn hopes of post-Ceaușescu society. Beyond the Hills, a study of the religious life and deep-seated psychological trauma, exposed the push-pull of the past and the future as the detritus of communism was being cleared away. Graduation, meanwhile, suggests the drift and uncertainty of a society unsure which way to turn.

Push-pull of the past … Mungiu’s 2012 drama Beyond the Hills. Photograph: Du Conseil D/Rex/Shutterstock

He points out that much of the content of Graduation comes from news stories he’s read in the past few years – a parent who tried to obtain preferential treatment for their children, a woman who was attacked in Bucharest but no one intervened. These things happen everywhere, all the time: “In life,” he says, “things just happen, they don’t have a meaning.” His job, he says, is “to try to preserve the ambiguity and complexity of the situation, then it’s up to you to figure out what this film tries to tell you about life.”

Mungiu talks a lot about “reality” and “truth” as he describes his cinematic project: the aim is to contain and distil some kind of authentic experience along with the demands of narrative. That is the ambition of every social-realist film-maker from Ken Loach downwards, but Mungiu can claim to have created a distinctive texture, with agile camerawork, harsh, unpretty visuals, unconventional editing, and an intense focus on character viewpoints. “I don’t jump from one character to another. We know as much as the main character knows; this is the way things happen in life. I won’t use music because there is no music in life, and I won’t signal to you as a spectator how to feel. It’s not fair. As film-makers, we can do better than this.”

• Graduation is released on 31 March.