For a filmmaker to get a swelled head when he scores an unexpected hit is not unusual.

It could easily have happened to first-time director Jeffrey Blitz, who recorded one of the great trifectas of the last decade with the spelling-bee documentary “Spellbound.” The 2002 film received universal popular and critical acclaim and garnered Blitz an Academy Award nomination to boot.

But the voluble, enthusiastic Blitz remains refreshingly down to earth, even as he makes the often-coveted crossover from docs to narrative features. “Rocket Science,” which opens Aug. 10, is a droll yet touching comedy about a New Jersey high school boy with a stutter who goes out for the debate team.

Hal Hefner’s motivation isn’t all that mysterious. He’s encouraged by the pretty, rich team captain, and we all know that a teenager will do some potentially embarrassing things when he has a crush.

Hal (Canadian actor Reece Daniel Thompson) isn’t identified as Jewish, but he gives off that vibe. Ben Wekselbaum (Nicholas D’Agosto), the previous team captain whom Hal desperately calls on for help, is unmistakably Jewish.

Blitz also stuttered in high school, although unlike Hal he went on to be a state-champion debater. He studied creative writing at Johns Hopkins University and film in graduate school at University of Southern California, where he became leery of autobiographical fiction. So Hal is not Jeffrey.

But did Blitz give him one identical characteristic — a Jewish identity?

“Gosh, you know what, I bet when I wrote the script I did,” the 38-year-old filmmaker

said during a recent interview at a San Francisco hotel. “I certainly thought of Ben that way, and I probably thought of Hal that way. But there comes a point when it starts to be inhabited [by an actor]. As soon as that happened, I let go of whatever my initial conception was of it.”

And yet, “Rocket Science” has a Jewish sensibility that you can’t quite put your finger on. Hal rarely catches a break, and claims our empathy from start to finish. At the same time, he’s too resilient and spunky to accept life as a shlemiel. In other words, he’s more of a comic figure than a victim.

Relating that his sense of humor is “a particularly Jewish” one, Blitz said, “When I wrote these characters, all of them, there’s a cadence and a sense of what’s funny that to me feels like it’s coming from a very Jewish place, and I think that’s what carries through.”

Blitz recalled how he and his brothers played a Woody Allen stand-up comedy record nonstop — even after it warped. And yet his Jewish home, with a father who’s a scientist and a mother who’s a doctor, wasn’t the most obvious place for a comic talent to bloom.

“My parents are very much people of the mind, and their value was in learning and in books and in experience,” he said. “Because their background is in science, they’re incredibly unfunny people. But they try — my dad tries to crack jokes endlessly — and one is worse than the next.

“But I think one of the hallmarks of a Jewish sense of humor is you can take people’s foibles and hold them up to laugh at but only to a certain point. You never cross a line so that you can’t connect to the heart of that person also. It’s all done in a loving spirit, even when there’s a lot of bite to it. And I think all the humor of this film is about that.”

While getting his master’s, Blitz was hired by the Writers Guild of America to research the uncredited work of writers blacklisted during the McCarthy era. It was a great job, he said, digging through basements, delving into archives and going around the world to read scripts, journal entries and letters.

A large number of blacklisted writers were Jewish, and Blitz learned an unexpected lesson.

“I would say that the impulse to define yourself with your back up against the wall — to figure out how to live through it — seems to be a particular part of the Jewish experience.”

While that doesn’t seem to be the case for Blitz, his “Rocket Science” is a movie that keeps audiences off balance, and is unlikely to turn into the phenomenon that “Spellbound” was. So the odds of Blitz becoming cocky and intolerable anytime soon are slim.

“Rocket Science” opens Friday, Aug. 10 in theaters throughout the Bay Area.