From the outside looking in, it seems like people stop offering constructive criticism once a filmmaker reaches a certain level of power in Hollywood. From a logical standpoint, that makes sense. Anyone who wants to keep working in the industry probably isn’t going to tell Scorsese that he’s making an iffy decision.

On the other hand, there’s a reason that kind of input is called “constructive.” Sometimes gently breaking the news that the script needs another polish — even if the people being told are J.J. Abrams and Steven Spielberg — can transform a pretty good movie into a great one. That’s what should’ve happened with “Super 8,” the duo’s latest tribute to the wonders of moviemaking and being a kid.

For most of the film’s running time, it plays like a tamer version of “Stand By Me.” It’s set in a small Ohio town in 1979 and centers on a group of childhood friends, including some who are forced to deal with the rougher aspects of life. However, at different points in the story Abrams (who pulls double duty as screenwriter and director) decides he’d rather be making a disaster movie or a sci-fi flick. Each of those plots might be interesting on their own, but jamming them all together makes the whole thing feel disjointed.

The story focuses mostly on Joe Lamb (Joel Courtney), a decent kid who just lost his mother in a steel mill accident. His lawman father (the always excellent Kyle Chandler) copes by throwing himself into the job, meaning his once-awkward relationship with Joe is now practically nonexistent. He desperately believes sending the boy off to baseball camp for the summer will fix everything.

Except Joe doesn’t want to go to baseball camp. He’s too busy having a blast as the makeup artist on his best friend Charles’ (Riley Griffiths) zombie movie. And once Charles talks Alice (Elle Fanning) into starring in his production, Joe has another reason — a taller, cuter and blonder reason — to spend the summer at home. She’s snippy with him at first (mostly because their dads hate each other for spoiler-related reasons), but she eventually becomes a genuine part of the gang.

The friends’ lives get even more complicated after they witness a giant train crash that kicks off a series of increasingly bizarre events in their town. Soon, a bunch of Air Force guys are running around everywhere, acting all ominous and secretive. Eventually, the kids realize they might already have the answer to the mystery thanks to the camera they’ve been using to make their movie.

Somebody (maybe Spielberg, who serves as executive producer and whose “Jaws,” “Close Encounters” and “E.T.” were obvious inspirations) should have reassured Abrams that “Super 8” would have worked just fine as a picture about a kid coping with the loss of his mother and a distant father, falling in love and making a zombie flick with his friends. He absolutely did not need train crashes or a mysterious creature. He wouldn’t have a summer blockbuster, true, but he’d have a much better movie.

Most of the story’s problems stem from a disjointed third act, which could’ve been avoided by removing the sci-fi stuff completely. I can’t get into specifics without spoilers, but you can feel the exact moments where Abrams cut-and-pasted two completely different scripts together. I’ll go out on a limb and say the flick could’ve been an Oscar contender if it had gone the low-key drama route.

I say that because of the fantastic performances delivered by the kids in the cast. Newcomer Courtney has the entire film resting on his shoulders, and he pulls it off admirably. There’s no trace of the over-enunciated line delivery typical of many child actors (like Adam Sandler’s fake daughter in “Just Go With It”) and he handles the story’s many emotional moments perfectly.

As great as Courtney is, he’s still outmatched by Fanning. She’s simply phenomenal as the headstrong girl who’s forced to grow up way too fast thanks to an absent mom and an alcoholic father. Fanning has been in several films and television shows over the last few years, but mostly seemed to be known for being Dakota’s little sister. Her work here should change that pretty quickly.

It would be unfair to fault “Super 8” for failing to be the movie I wanted it to be. However, I can be disappointed that Abrams failed to realize he could’ve made a much stronger movie than he did. Though it’s a deeply flawed film, it’s still an admirable one that’s worth seeing. At least it’s not a sequel, a remake or based on a comic book.

“Super 8” is rated PG-13 for intense sequences of sci-fi action and violence, language and some drug use.