Patrice Chéreau fervently believed in actors. Performances were a production’s aorta, its life source, its raison d’etre. Guided by this principle, Chéreau, the legendary French director who died in 2013, used his stage work and films to agitate, wrestle and contend with the mystical relationship between actors and their characters.

His most rigorous application of this philosophy might have been during his years as director at Théâtre des Amandiers in Nanterre, France, where he founded the acting school and film studio. Appointed in 1982, Chéreau spent a decade at Amandiers, shaping a coterie of actors. He was a combustible figure; his temper easily flared, his demands famously exacting. But the school was an unparalleled training ground for aspiring performers. There, they could embody — not just learn — the tenets of their craft.

Such intense environments inspire rumors of mythic proportions. In Forever Young, the Italian-French actress Valeria Bruni Tedeschi examines Chéreau’s Amandiers years. As with her previous directorial features (this is her fifth), her interest in the subject is driven by the personal: Bruni Tedeschi was a student of the exclusive school, and her first film role was in Chéreau’s 1987 drama Hôtel de France, which premiered at this festival.

But proximity is a double-edged sword when it comes to reflection. How does one look back without succumbing to nostalgia’s traps or hindsight’s dishonesty? Forever Young ­inadvertently studies these questions. It’s a sweet but oddly circumspect film, ruled by a friction between warring demands: the allure of wistful memories and the rigor of complex appraisal.

Bruni Tedeschi’s film follows a group of Amandiers students in the late ’80s. They are a stylish group, eager to prove themselves to Chéreau and to each other. It’s not long before they realize, however, that their time at this school will be more than just a competition for roles or an endurance test for their capricious director’s moods. Like the characters in Donna Tartt’s novel The Secret History, they have entered into an intimate world, a community resembling a cult.

The film opens with a grueling first round of auditions, a brisk montage of young hopefuls hurling their lines, flinging their bodies and engaging in chaotic levels of theatrics. A largely unimpressed clique of instructors sits before them. Chéreau (Louis Garrel) is not present. He likes to keep a low profile, according to his assistant director Pierre Romans (Micha Lescot).

At the end of the audition, each student must answer one question: Why theater? The question is one of the film’s insistent themes. Some bare their tortured souls; others aim for subtlety or humor. The responses are colorful, cloying, cringey. This film isn’t just about a particular cohort; it’s about acting, too.

And what exactly is acting? Is it a misguided pursuit of madness, as one character says early on? Is it an exercise in vanity? An attempt to retain the vivacity of youth? Or is it more sentimental? Noble, even? Bruni Tedeschi, who wrote her screenplay with Noémie Lvovsky and Agnès de Sacy, excitedly prods these existential questions through a troupe of budding thespians.

Stella, a talented, credulous and wealthy young woman played by Nadia Tereszkiewicz, is the first person we meet. Her skills are evident from the beginning, and her bubbling enthusiasm, too.  She comes off younger than she appears, wearing an interest in the world that borders on naïveté. After her audition, she clumsily beelines for the bathroom where she runs into Adèle (Clara Bretheau), a snappy and impulsive redhead.

The two become instant friends, forming a bond that I wish got more play throughout the film. They meet the rest of their class on admissions day. It is an unceremonious event, consisting of students nudging their way to Amandiers’ main entrance, where a list with 12 names is taped onto the door. The scene, like the auditions, is stuffed with drama and emotion. Students shriek at news of acceptance and burst into tears over rejections. Some desperate ones chase down instructors, begging for another chance.

But the decisions are final. The chosen class includes Stella and Adele; Etienne (Sofiane Bennacer), a talented drug addict haunted by a painful childhood; Franck (Noham Edje), a hopeless romantic with a baby on the way; and Camille (Alexia Chardard), a pregnant student determined not to sacrifice her dreams for motherhood.

The cohort bonds quickly. They party, cry, have sex, laugh and panic together. The performers Bruni Tedeschi has assembled are an arresting bunch, who inject their broadly sketched characters with an impressive amount of life. Even minor figures get serious treatment, as if these performances are speaking directly to Chéreau’s philosophy.

A class trip to New York plunges the students into the world of modern performance and imbues them with a sense of what is possible in acting. Again, they are forced to confront the question: Why theater? Answers to that query change as the students deepen their understanding of their craft and its costs.

This interesting exploration is, somewhat unfortunately, only a fraction of the narrative’s concern. At the core of Forever Young is a love story between naïve Stella and brooding, troubled Etienne. Their characters aren’t particularly distinctive, but Tereszkiewicz and Bennacer are fine performers who confidently maneuver the material. The couple fight, break up and make up at a dizzying speed; DP Julien Poupard favors close-ups, giving those scenes an unnerving intimacy. The clichéd relationship is doomed from the start, though there is something admittedly captivating about watching a predictable trainwreck.

But it’s a difficult enthusiasm to sustain, and as Stella and Etienne tread a familiar romantic path, the story starts to slacken and indulge. Other plot points get some air — the pregnant student’s ambitions, another’s antagonistic relationship with Chéreau, the looming AIDS crisis — but there isn’t enough time spent on any single one to meaningfully earn our investment.

There’s also a lack of subtlety that begins to grate after a while. The constant telegraphing, whether through Poupard’s otherwise superb camerawork or the screenplay, signals, at least to this critic, a curious lack of trust in the viewer’s ability to keep up with the narrative.

Forever Young is at its strongest when it returns to the question of why theater and engages with Chéreau’s relationship with his students. In these scenes, the director’s process takes center stage, inspiring questions about the cost of his methods. When Forever Young shifts its focus away from Etienne and Stella and to the class production of Chekhov’s Platonov, it feels keener, fresher in its insights and perspective.

The rehearsals sizzle as the students and Chéreau manage (or fail to manage) their increasing levels of stress and escalating tensions. A sense of community emerges under Chéreau’s asphyxiating rule. His instructions are involved and precise, his moods unpredictable. Garrel is excellent as the flawed director, channeling a man whose obsession with perfection masked some cruel behavior.

It’s when Forever Young moves beyond the familiar melodrama of youthful love that it begins to tap into more authentic territory: the demands of a still-misunderstood craft and the blurred line between life and performance.