"Never work with children or animals."

That quote is attributed to famed actor-comedian W.C. Fields, but it now belongs to all of show business as a humorous – and often accurate – piece of advice. See "The Last Airbender" or "Star Wars: Episode I." Then again, you could Frankenstein the talents of young Mary Badham, Jodie Foster, Tatum O’Neal and the kids from "Moonrise Kingdom," and those scripts would still come off wretched.

From performance quality to production concerns, relying on child actors is a risk or reward proposition. In the case of "The Inevitable Defeat of Mister and Pete," the latest from director and native Milwaukeean George Tillman Jr., the results land firmly in the latter. Youngsters Skylan Brooks and Ethan Dizon end up being the best thing Tillman could’ve asked for, electrifying the film and giving the story the heart it needs.

Right from the opening moments, things are looking grim for Mister (Brooks). He’s failed the eighth grade, and his mother (a shockingly haggard Jennifer Hudson) is a resigned servant to her drug addiction and her pimp/drug dealer (Anthony Mackie). As things reach the breaking point between Mister and his mom, the police come knocking and take her away. Now, during a punishing summer heat wave, Mister must take care of himself and Pete (Dizon), his quiet Korean neighbor whose junkie mother – seen for just a fleeting moment – ran off.

The two scrape up whatever food they can to stay alive and avoid getting caught by the police – led by an intimidating Adewale Akinnuoye-Agbaje – and sent to a boys’ home with a history of violence. This means panhandling on the street next to an ornery homeless man (Jeffrey Wright) who may or may not be a war vet, and battling with an Indian corner store clerk (Kenneth Maharaj) who hasn’t taken kindly to Mister’s attitude.

And as the sweltering days drain the boys’ bodies and resolves, it seems more and more like Mister’s mom may have taken the same route as Pete’s and bailed. Jordin Sparks from "American Idol" also appears as a kind friend from back in the day who’s moved out of the projects.

Even with a cast of some of Hollywood’s finest actors surrounding them (they’re mostly supporting roles with two or three scenes each), the film’s success instead rests almost entirely on young Brooks and Dizon. And though they look frail on screen (shockingly so as it goes along), their performances are strong enough to carry the film to success.

Dizon gets the easier and more crowd-pleasing of the two roles as Pete, who basically becomes Mister’s little brother. He’s sweet, adorably articulate and still innocent despite all the world’s thrown at the little loner. At one point, he quietly reveals to Mister a history of sexual abuse from his neighbor. Later, he shows a brutal iron burn on his back. It’s a role that could’ve come off forced or saccharine, but Dizon is just the right amount of charm.

Brooks, though, is the real revelation. The young actor is a powerful fury, playing a hurt, vulnerable and even hopeful young boy hidden under a mask of stubborn self-confidence. When we first see Mister, he’s sobbing about failing in school. Minutes later, when his teacher offers his help, Mister verbally spits it back in his face. He’s not a bad or a lazy kid; he wants to do better. He’s simply grown up learning he’s the only one he can rely on, and that a backbone – even if it’s just a child’s – is the only way to survive in an unforgiving world.

He’s strong in his will to survive, but Brooks always shows the desperate uncertainty of a lonely child fighting its way to the surface. It’s a mature performance, but one that never forgets the character is still a kid. And when there’s a rare moment of youthfulness (like a makeshift game of bowling using Pete’s hamster in a ball), Brooks’s joy feels so satisfying, not only because it feels real but also because it’s been so hard earned.

Their compelling lead performances and their slow bond end up providing the emotional impact the rest of "Mister and Pete" is strangely never quite able to summon. It’s not Tillman’s fault, as his direction – an energetic mix of grit and warmth – fits the material nicely. His work is just the right amount tension and sentimentality.

It’s hard to pinpoint exactly why the film doesn’t quite hit as hard as it should. It might be the occasionally relentless story from writer Michael Starrbury (another Milwaukee native) that seems to pile on five tragic moments for every one remotely pleasant one. Or maybe it’s the script’s tendency to give moments – like the boys’ brief run-in with Pete’s mom – just a bit too much punctuation. The movie doesn’t quite yank on the heartstrings, but I could certainly feel a tug that I wish was just a bit more delicate.

Even if the whole isn’t great, though, the parts certainly are, especially Brooks and Dizon. In a film with plenty of great pros, it’s the kids that own the screen and, in the end, make "The Inevitable Defeat of Mister and Pete" a winner.

Take that, Mr. Fields.

"The Inevitable Defeat of Mister and Pete": ***