LOS ANGELES — An anti-bullying allegory writ on the largest possible scale, “Ender’s Game” frames an interstellar battle between mankind and pushy ant-like aliens, called Formics, in which Earth’s fate hinges on a tiny group of military cadets, most of whom haven’t even hit puberty yet.

At face value, the film presents an electrifying star-wars scenario — that rare case where an epic space battle transpires entirely within the span of two hours — while at the same time managing to deliver a higher pedagogical message about tolerance, empathy and coping under pressure. Against considerable odds, this risky-sounding Orson Scott Card adaptation actually works, as director Gavin Hood pulls off the sort of teen-targeted franchise starter Summit was hoping for.

Card’s novel assumes a situation where, in the wake of a massive Formic attack, the world’s children are somehow best suited to protect their planet from an imminent second strike. The most promising young recruits train on elaborate videogame-like simulators while a pair of officers — Col. Hyrum Graff (Harrison Ford) and Major Gwen Anderson (Viola Davis) — monitor their techniques in search of “the One,” a child with the strategic instincts to save his species. The leading candidate is Ender Wiggin (Asa Butterfield), a runt-like outsider whose behavior toward his aggressive classmates reveals his true potential.

Like “The Hunger Games,” the pic peddles the unseemly idea of watching kids thrust into life-and-death situations. Though they’re not instructed to kill one another, these moppets’ prime directive should also give parents pause, raising the stakes from hand-to-hand combat to the potential genocide of an unfamiliar race.

Butterfield makes ideal casting for Ender: He’s scrawny and physically unimposing, yet there’s an intensity to his stare that suggests he might indeed be masking deeper (or darker) gifts.

Despite the obvious “be all you can be” subtext, “Ender’s Game” manages to make training sequences compelling without veering into pro-military propaganda, doing so by focusing on the interpersonal dynamics between the various squad members. Though Card may have publicly revealed his own prejudices, the casting department has assembled a wonderfully diverse group of young actors — male and female, they come in all colors, shapes and sizes — to serve alongside Ender.

So much youthful energy on-screen makes Ford seem tired and weary by comparison. Butterfield’s “Hugo” co-star Ben Kingsley also pops up for a late cameo. It might not seem fair to compare what Hood has created to someone as visionary in all things sci-fi as George Lucas, and yet, considering the sizable budget expended on “Ender’s Game,” one could have hoped for something a bit more groundbreaking.