Being 17 seethes with the unrestrained volatility of its adolescent protagonists and could easily be mistaken for a wunderkind filmmaker’s first film. In fact, it’s a late-career masterpiece made by André Téchiné. A 73-year-old Frenchman, he once wrote for Les Cahiers du Cinéma, the magazine that helped launch the careers of New Wave directors like Godard, Chabrol, and Truffaut. He co-wrote this script with Céline Sciamma, a young filmmaker known for her insightful work about teenagers (Girlhood, Water Lilies). She must have been enamored of his summery film Wild Reeds (1994) because much of that movie’s urgency informs this story. The camera watches Damien (Kacey Mottet Klein) and Thomas (Corentin Fila) as they watch each other. It closes in on their confusion and their impassioned rages as they prowl the school corridors. When Thomas’ mother (Sandrine Kiberlain), a doctor, helps Damien’s ailing mother, she also unknowingly alters the course of the boys’ relationship. The phrasing of the original title — Quand on a 17 ans — promises a nostalgic look at that age between youth and adulthood. But Téchiné’s unabashed lyricism has hardened in the last 20 years. He fills the screen with wintry images: a black lake, leafless trees, a cave of shadows. This barren landscape becomes a proving ground, where bruises can heal and transform into the most durable kind of love.