Kayla (Elsie Fisher) is in the final stretch of her middle-school experience, and all she wants to do is make it through in one piece. An introverted 13-year-old girl socially awkward in her attempts to fit in, she isn't bullied so much as she is simply ignored by most of her peers. At home, she makes YouTube videos with slightly more confidence, aiming to spread inspiration to viewers on topics affecting adolescents in her age range, but really just hoping her words might have a positive effect on herself. When she is chosen as "Most Quiet" in her graduating eighth-grade class, it is but a bitter reminder that she is an outsider among classmates who act as if they have everything already figured out. The accomplished writing-directing debut of actor-musician Bo Burnham, "Eighth Grade" is a stirring, painfully accurate slice-of-life, the kind of film so authentically observed it sometimes feels more like a cinéma vérité documentary than a scripted feature film. Selling this illusion all the more is Elsie Fisher, whose past credits (including voicing Agnes in 2010's "Despicable Me" and 2013's "Despicable Me 2") were clearly appetizer for the breakthrough lead performance she delivers here. She is nothing short of magnificent in a demanding, front-and-center role requiring significant layers of vulnerability and courage.

For every moment, the viewer tags alongside Kayla, silently rooting for things to go well for her while occasionally growing frustrated by the natural teenage moodiness she directs at her single father Mark (Josh Hamilton), an upbeat guy struggling to do his best as a parent. Credit must go to Burnham for his understanding that it's the small moments which often sting hardest—how, for example, Kayla bids a quiet congratulations to classmates who pass her by without acknowledgment, or the way the snooty Kennedy (Catherine Oliviere) opens Kayla's birthday present and quickly disregards it without so much as a 'thank you' at the pool party she's forced to attend. Meanwhile, the repetitive days of sameness tick by amidst the droning halls of middle school. At a sensitive age when she is too old to be into children's play yet still too young to be romantically comfortable around boys, Kayla briefly catches a glimpse at how much better the years ahead might be when she shadows friendly high school junior Olivia (Emily Robinson) for a day. Olivia very well might have been like Kayla a few years earlier, and when Olivia invites her to hang out with her group of pals at the mall, Kayla's jubilation becomes our own, just as insecurity rears its ugly head when it becomes clear she cannot quite connect with these older kids.

Perhaps the most impressive hurdle Elsie Fisher jumps is in never revealing that she's acting at all. Kayla's opening YouTube video, one whose message is very nearly overshadowed by her nervous overuse of "um" and "like," feels uncomfortably real, as do the gradually improved subsequent ones. These monologues, viewed as windows to her own real-time internal battles, tellingly inform her everyday travails as a virtual wallflower trying to put her own advice about being more outgoing and embracing one's individuality into action. Fisher is understated and moving as Kayla, seemingly incapable of striking a false note. Josh Hamilton (2013's "Dark Skies") gives Kayla's dad Mark a sympathetic grace of his own. With good humor and a tinge of sadness, Mark tries to connect with his daughter precisely at an age where she is pulling away and yearning for more independence. A late scene between Hamilton and Fisher where Mark expresses to Kayla how special she is and how proud he is to be her father is beautifully written and performed, an incisively earned emotional catharsis.

It is no secret one's middle-school years are typically miserable—it is during this time when we are going through the most physical and biological changes, all while still struggling to find ourselves and evade the wrath of our peers—and throughout "Eighth Grade" writer-director Bo Burnham captures this precarious period with impeccable, aching authenticity. That Kayla is so actively, messily striving to better herself, to break out of her shell and also stand up for herself when she feels slighted, is worth cheering. It's these victories, however small, which inform the fully formed person she is becoming. As much as she might try, though, Kayla cannot be anyone other than who she is, and there is a raw, identifiable honesty in the film's portrayal of a person stricken with social anxiety. For all of the struggles she's faced and the heartaches still in front of her, beyond all the self-involved "popular kids" living in their self-absorbed bubbles, there is little doubt she will make it out the other side okay. As eighth grade comes to an end, Kayla creates a time capsule, not unlike the one she made three years earlier at the start of middle school. Written atop the box, just like her sixth-grade capsule, is a declaration she deserves to always hold onto: "The coolest girl in the world." Gucci!