To fight or to fall in love: That is the choice two antagonistic high school classmates face in “Being 17,” a touching drama about raging hormones, bullying and sexual awakening — and the strongest film in many years by the post-New Wave French director André Téchiné.

Even when punching each other furiously, Thomas (Corentin Fila) and Damien (Kacey Mottet Klein), combatants whose senseless schoolyard fights have an undertone of repressed desire, wear the stricken expressions of innocents caught up in a war they don’t understand and would rather not fight.

The film follows their conflict over three academic trimesters. Their scuffles begin as pranks by Thomas, who trips and shoves Damien in surprise attacks. The matches become increasingly brutal and ritualistic, inflicting injuries.

The two could hardly be more dissimilar. Thomas is the adopted biracial son of sheep and cattle farmers in the Pyrenees. Damien is a spoiled, high-strung son of Marianne (Sandrine Kiberlain), a doctor from the valley below, and her husband, Nathan (Alexis Loret), a helicopter pilot in an unidentified war zone. The family keeps in touch via Skype. In one of her strongest performances, Ms. Kiberlain’s Marianne is a dedicated physician who goes out of her way to help others and has no qualms about exerting authority.

While Thomas struggles with his schoolwork, Damien is an academic star, math whiz and arrogant nerd who in his spare time takes classes in self-defense. Thomas’s visceral hostility is exacerbated by Damien’s air of superiority and by the rhinestone earring he wears. But in the high school pecking order, both are outsiders.

Marianne makes a house call to Thomas’s farm when his mother, Christine, has a pulmonary infection, and discovers that Christine, who has a history of miscarriages, is pregnant. Unaware of Thomas and Damien’s mutual hostility, she invites Thomas to stay in her house so he can avoid the daily three-hour round-trip commute, much of it on foot, and she coaches Christine through her pregnancy.

Once Thomas has moved in, Damien, the more articulate of the two, nervously confesses, “I don’t know if I’m into guys or just you” and initiates a first embrace, which Thomas seems to welcome before recoiling.

Notes of magical realism are threaded through the movie. One night in the mountains, Thomas strips naked and dives into an icy lake while Damien watches, entranced. In another scene, Marianne, whose husband is away on a combat mission, has an erotic fantasy in which Thomas makes love to her. Such moments give “Being 17” a semi-mythological dimension. At one point, late in the movie, the boys exchange literary quotations about desire.

Scenes of Thomas pitching hay and brushing cattle underline the suggestion that he is a symbolic force of nature exerting a gravitational pull. As he tramps through the snow on his way to school, you have a piercing sense of a young man in harmony with nature. In certain shots, he is almost heartbreakingly beautiful, yet unaware of his charisma.

“Being 17” is Mr. Téchiné’s first screenwriting collaboration with Céline Sciamma, whose films “Water Lilies,” “Tomboy” and “Girlhood” address gender and sexuality with a contemporary immediacy. The movie is not really about deciding whether you’re gay or straight — those terms are never spoken. It’s about the chemistry of two people at a moment in time.

“Being 17” is not rated. It is in French, with English subtitles. Running time: 1 hour 54 minutes.

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