Tina Fey and Paul Rudd star in Paul Weitz's comedy/drama ADMISSION. (David Lee / Focus Features)

Like an anxious parent waiting to hear whether his kid has gotten into a good college, I worry about “Admission.” I worry that the quirky little film — which stars comedians Tina Fey and Paul Rudd but is not exactly a “Tina Fey and Paul Rudd comedy” — might never find its true audience. I worry, in short, that it’s a classic example of the cinematic underachiever: a movie with a good head on its shoulders and a sweet heart, but with an inconsistent report card, based at least on the mixed reaction at a recent screening.

There’s a high school senior with the same problem at the center of this off-kilter charmer, directed by Paul Weitz from screenwriter Karen Croner’s adaptation of Jean Hanff Korelitz’s serio-comic novel. That’s Jeremiah Balakian (Nat Wolff), a brilliant oddball with a lousy GPA who got stellar scores on his SAT and AP exams. Rudd plays Jeremiah’s principal, John Pressman, an earnest free spirit who’s so determined to get his misfit star pupil into a good school that he calls up his old college classmate Portia Nathan (Fey), a Princeton University admissions officer.

John also has discovered — or believes he has discovered — a familial connection between Portia and Jeremiah, an adoptee who is the same age as the child Portia gave up for adoption when she was an undergraduate. Believing that she is Jeremiah’s birth mother, Portia’s maternal instinct suddenly kicks in.

That complicates her job, which depends on her ability to accept or reject an applicant based not on emotion, but on quantifiable academic suitability.

Have I mentioned that “Admission” is not especially funny?

The trailer can’t seem to make up its mind. On the one hand, it looks like a satire of academia. On the other hand, it could be a gentle rom-com. In truth, it’s neither.

Or rather, it’s both, to some degree. Mostly, it’s a tale of regret and letting go, and how the paths that our lives take matter less than the way we walk them. Like Weitz’s excellent “About a Boy,” “Admission” is a serious film about life, relationships and growing up, with a gloss of humor.

On paper, some of it actually sounds quite heavy. Portia’s tart-tongued feminist mother (Lily Tomlin) has just undergone a double mastectomy. John is a single father, struggling to raise an African orphan (Travaris Spears). And Portia’s live-in boyfriend (Michael Sheen) unceremoniously dumps her early in the film.

Although Weitz and Croner keep things light, there’s a groundedness to the film, thanks largely to the fine supporting cast, which includes Wallace Shawn as Portia’s nebbishy boss, who is considering naming her as his replacement when he retires.

In their central roles, Rudd and Fey have a natural, unforced chemistry. John and Portia are cute as buttons, but they’re also goofy, confused and flawed people. So is Jeremiah. Wolff, a juvenile actor who cut his teeth on the Nickelodeon TV series “The Naked Brothers Band,” really comes into his own here.

I’m not surprised the trailer seems to misrepresent “Admission.” It’s difficult to pigeonhole. A little too quirky for the multiplex but too mainstream for the art house, the movie could very easily get lost in the shuffle.

And that would be a shame. I feel the same way about it as the Princeton professor who’s asked to give Jeremiah a recommendation, based on the boy’s performance of an awkward ventriloquist skit inspired by philosopher Rene Descartes.

“Weird,” the professor says, shaking his head. “I liked it.”

PG-13. At area theaters. Contains obscenity and some sexual situations. 110 minutes.