When we first meet Kayla Day, the introverted but indomitable protagonist of the film “Eighth Grade,” she’s delivering a YouTube tutorial, one of a series she’s been working on that deal with such perennial adolescent vexations as confidence and self-esteem.

Today’s lesson is on “being yourself” and, in a painfully tight and pixelated close-up, Kayla explains why that’s a good and even necessary thing, even though, umm, you know, like, people suck and evil exists. “You just have to ignore them,” Kayla concludes, the camera having pulled back enough for the audience to understand that this pep talk, like all the others, is more intended for herself than her nonexistent audience.

In a raw, radiantly generous performance by Elsie Fisher, Kayla joins the pantheon of great teenage heroines. “Eighth Grade” takes place during the last week of middle school, as the pimply, perpetually slouching Kayla says goodbye to her childhood and warily takes the next steps toward bona fide teenagerdom: In the course of an eventful few days, she’s put through all manner of tests, literal and figurative, as she and her classmates participate in a live-shooter drill, accept their “superlative” awards (Kayla wins most quiet), throw pool parties and take an orientation trip to their future high school.

With the camera following Kayla like a hovering mother hen, we watch as she tries (and mostly fails) to connect with her would-be friends, arriving at said party with a lame birthday present, and making awkward small talk with her crush, an oblivious, sleepy-eyed fox named Aiden (Luke Prael).

In many ways, “Eighth Grade” isn’t a coming-of-age story but a study in the tyranny of influence and social panic. But it’s also a compassionate and sneakily effective portrait of its antidote. As painful as Kayla’s isolation is, as cringe-y as it is when she’s rejected, she’s never truly abandoned in a film that ultimately rejects dwelling on cruelty, choosing instead to reward the character and the audience with moments of genuine kindness, and finally pulling the lens all the way back to remind us that “Eighth Grade,” like the rite of passage it chronicles, is merely a moment in time.

Kayla might be lonely and miserable, but she’s far from hopeless. As an avatar for selfhood — not as a fixed point or a performative act, but as a state of constant becoming — she’s already on the move. And she’s a thing of sheer beauty.

Starring Elsie Fisher, Josh Hamilton, Emily Robinson, Luke Prael; directed by Bo Burnham; 93 minutes; R for coarse language and some sexual material.

Elsie Fisher as Kayla, a great teenage heroine, in “Eighth Grade.”

courtesy of A24