Most coming-of-age stories are designed to tickle our nostalgia bone, to conjure up the myths we tell ourselves about our teenage years. They’re not supposed to tell the truth. Measure of a Man may be one of those false narratives, but at least it earns its lies. It spends so much time in the land of normal teenage life that its cathartic ending is the kind of sweet release that only the best coming-of-age films can provide.

Bobby Marks (Blake Cooper) is a fat kid. This is not a judgment or a slur; it’s how he is defined by all who know him. His problem isn’t that people can’t look past his weight to see the great guy inside. Rather, he hasn’t yet developed into a great guy because he is hiding from shallow eyes. He “hates summer vacation,” we are told in painstaking voice-over, probably because he’d rather be inside reading his Archie comics than outside working, which is what his parents (Judy Greer and Luke Wilson) force him to do.

He ends up doing landscaping for an eccentric rich guy (Donald Sutherland), whose intentionally muddled accent speaks of a mysterious past. It’s a supporting role designed for a star to give the film some marketability, and his scenes are the weakest the film ever gets. He’s a Magical Fogey who dispenses wisdom and dollar bills to Bobby in exchange for terrible lawn mowing. Meanwhile, Bobby becomes the target of some local bullies, including the dangerously violent Willie Rumson (Beau Knapp), who resents the influx of rich city folk to their once-mellow lake named after his great-grandfather. There’s also a girl, of course, his summer friend Joanie (Danielle Rose Russell), who he wishes to turn into his summer girlfriend.

Does it all sound a little trite? It is, but that’s not the worst crime for a film with such sweet, simple aims. Measure of a Man doesn’t seek to reinvent the genre, nor even to reinvigorate it. There is nothing edgy or new about it. Instead, its charm is in how little it tries to impress.

Director Jim Loach (son of British filmmaking legend Ken Loach) never tries too hard to make us laugh or cry. Instead, he presents the story with few flourishes, which somehow underlines its importance and makes it feel all the more special.

At the crux of our attention is Cooper, who had a memorable role in The Maze Runner (if, that is, you remember the movie), but acquits himself even better here as an average kid who has yet to be convinced that his life is in any way special. Bobby endures some tense, life-altering moments during his summer by the lake, but Cooper never overplays his hand. He swallows his words and fumbles his grand gestures, yet he offers glimpses of the man he’s yet to become.

It’s a deceptively powerful performance, and although it is not enough to elevate the entire genre, it nonetheless separates Measure of a Man from its competitors. Summer vacation is about to get a lot better.

Measure of a Man opens Friday at the Angelika Pop-Up at Union Market.