Toni is an 11-year-old amateur boxer who works out daily with her attentive older brother in a West Cincinnati recreation center. Quiet and determined, her studied focus is pulled one day by the sight of a gaggle of confident older girls congregating down the hall. Spying on them, she discovers that they are drill dancers, practitioners of a form of competitive performance that is every bit as demanding and disciplined as fighting, and about twice as aggressive.

“The Fits,” an extraordinary feature debut from writer-director-producer Anna Rose Holmer, follows Toni as she loosens the ties that bind her and tentatively explores dancing, coming under the tutelage of her curvy, worldly teenage mentors and forming a joshing alliance with a limber little sparkplug named Beezy. Played by the aptly named Royalty Hightower in an astonishingly assured turn, Toni is that cinematic heroine so many viewers crave and so rarely see: a serious, self-possessed young woman whose coming-of-age, in this instance, has nothing to do with boys, sexuality or the outside forces that constantly threaten to negate her very being. Rather, in this modestly scaled allegory of female competition and contagion, Toni simply navigates — with supreme poise and inner calm — the precipice between not-quite-childhood and not-quite-adulthood.

That psychic outcropping is made more treacherous in “The Fits” by a series of convulsions that beset the older teenagers observed from afar by Toni and Beezy (played with scene-stealing adorability by Alexis Neblett). At once ethereal and grittily enigmatic, Holmer’s world is almost entirely populated by young people — we never see Toni’s mother — who drift and dance across the screen with grace and purpose. In addition to her exquisite eye for casting, Holmer knows how to film actors and environments in ways that are expressive enough to make up for her minimal dialogue. (Holmer filmed “The Fits” on location in Cincinnati and photographs the city with thoughtful, understated elegance: In one scene the camera rests pointedly on the sign outside the recreation facility which is called, appropriately, Lincoln Center.)

Lauren Gibson as Maia (left), Royalty Hightower as Toni (center) and Alexis Neblett as Beezy (right) in “The Fits.” (Oscilloscope Laboratories)

What, exactly, are the fits of the title? Are they simply adolescent hysteria or do they portend something more menacing? (The film’s electronic score, by Danny Bensi and Saunder Jurriaans, often suggests the latter.) Holmer never gives viewers a direct answer, instead inviting them to reflect on their own childhoods, and the strange, seductive yet frighteningly fatalistic experience of growing up. Although “The Fits” has nothing to do with pulp chills or exploitation tropes — and perhaps because it’s opening just a week after the documentary “De Palma” — it might remind some audience members of “Carrie” in its foreboding tone, its wary portrait of teen-girl culture and, finally, its exhilarating depiction of a girl claiming her power, not by any supernatural means, but through her own formidable sense of self. “The Fits” and its electrifying young star give getting in formation renewed meaning, with inspiring, self-assured verve.

Unrated. At Landmark’s E Street Cinema. Contains mild action, rude humor, and some profanity. 72 minutes.