When it happens, your heart sinks, and maybe an “Aw, dude” crosses your lips.

Up until that moment, which we see coming, you could cling to the hope that Coach Fred was going to keep things professional with his new star skier. He’s tough, but motivating, clumsily nurturing when coaching, mothering and fathering his unmoored, unworldly young charge.

Lyz is alone, estranged from her father, disconnected from her mother, almost friendless at this academy where French Olympic hopefuls polish their downhill skills. She’s under enormous pressure. This 30something jerk can’t control himself around her in the worst way.

What 15 year-old should face this?

“Slalom” is a quiet tragedy ripped straight from any week’s sports headlines. In a culture where success in sport is so prized that we allow its pursuit to begin early and expect maturity in the still-childish, Charlène Favier’s harrowing drama lives in the fragile psyche of a star-in-the-making, a victim before she knows what hit her.

Noée Abita is Lyz Lopez, whose loveless good-bye from her mom tells us all we need to know.

“You’re lucky, you know?” (in French with English subtitles).

Lyz has been selected for the FL Alpine club, one of many such operations that polish talent and feed the French National Ski Team and its Olympic dreams. And she’s told, straight off, that she’s too soft to have much hope.

Fred (Jérémie Renier) clinically sizes her up, measures her body fat and shames her about her weight as he challenges her. “You’re a bit behind the others.”

When they’re in a team setting, he’s not shy about berating her.

“Don’t be as s— as her,” he tells her teen teammates.

Lyz doesn’t break, but we see the vulnerability. She’s got nowhere to go on weekends, as her mother (Muriel Combeau) is in Marseilles and living her own life. Dad might be good for child support, but probably not and he’s certainly good for nothing else.

Lyz finds herself leaning on coach and the academy’s teacher, Lilou (Marie Denarnaud), the couple who run FL. She wants “to make it to the top,” so she puts up with the insults, the side-eyes from teammates as she starts to show promise and steals all the the attention of her coach, who is stern and clinical but, we can’t help notice, a little handsy.

As we’ve learned from a hundred scandals and many a sad athlete biography, that’s a power dynamic ripe for disaster.

Abita, a bit player in “Sink or Swim” and support in “My Days of Glory,” ably summons up the misguided confidence and sullen disappointment of teenagerdom. We buy Lyz’s acting-out even as we fear how far she will take it, because she seems genuinely unconcerned with the risks she starts taking.

Are we seeing classic signs of hidden abuse, the deflated heartbreak of infatuation, or a painfully subtle blend of both?

Renier, who’s been around since before “In Bruges” and was in “Frankie” a year or two back, doesn’t play the lip-smacking villain here. He lets us see confusion as Fred idiotically thinks he can cross a line and then step neatly back over it, because he’s allegedly an “adult.” We cannot tell if he’s done this before, or if his self-control collapses because he’s finally landed himself a winner, one who looks like a young Mila Kunis.

Director and co-screenwriter Favier, making her feature debut, gives us scenes of icy intimacy and striking racing footage. We’re totally convinced Lyz is too young to get a handle on what’s happening to her, and reasonably convinced Abita/Lyz is as good on the slopes as everyone is saying, even if she doesn’t have ski-racing thighs.

The helmet-off moments after each race lack any sense of flushed, foggy breathlessness. If you’ve ever watched a Winter Olympics, you know what I’m talking about.

But those are tiny quibbles in a movie that takes a very sober look at something that is a major scandal in sport, something that should give any parent pause before they sign off on a child’s dream pursuit of athletic glory.

MPA Rating: unrated, sex, drinking and smoking, all involving an under-age teen.

Cast: Noée Abita, Jérémie Renier, Marie Denarnaud, Muriel Combeau, Maïra Schmitt

Credits: Directed by Charlène Favier, script by Charlène Favier, Marie Talon and Antoine Lacomblez. A Kino Lorber release.

Running time: 1:32