Kid-friendly funnyman Kevin James is at his cuddliest in “Here Comes the Boom.” And he has to be. This amusing but sometimes unsettling comedy marries the teacher-turns-to-mixed martial arts mayhem of “Warrior” to that wholesome family dramedy “Mr. Holland’s Opus.”

It works, after a fashion. But that doesn’t mean you won’t wince.

James plays Scott Voss, a Boston high school biology teacher who is a decade past his “Teacher of the Year” days. He’s a burnout, habitually late for class, not shy about telling even that rare eager student (Filipino singer-actress Charice) that what he’s teaching and what they’re learning “just doesn’t matter.”

But he’s touched by seeing that rare colleague who is still inspired and inspiring. And when put-upon Mr. Streb (Henry Winkler) and his music program are the first things on the chopping block when Principal Betcher (Greg Germann) has to slash the budget, Scott is moved to act. He’ll raise the $48,000 needed to save his friend’s job and his orchestra.

Bake sales won’t be enough, as the fetching school nurse (Salma Hayek) discovers. And part-time work teaching citizenship classes to immigrants won’t raise much cash, either. But that collision with a collection of semi-stereotypes is where Scott meets the gregarious Niko, played with an amateurish verve by martial artist Bas Rutten.

Niko may teach “disco street fighting” classes at the swanky health club down the street. But he used to be a mixed martial arts fighter.

Scott convinces this Dutch (the accent comes and goes) brawler to train him so that he can get into the ring — the octagon — take a beating, and get paid for it.

Which is what he does, running afoul of school policy and impressing the nurse, whom he flirts with constantly.

James is in fighting trim here, the latest in a line of overweight yet graceful funnymen. He’s developed a comfortable screen presence that takes away the impression that he was working too hard for laughs.

Winkler has his best role since, what, “Night Shift”?

And James, Winkler, Hayek and Rutten make an amusing ensemble and click together. The importance of high school music programs is emphasized, the struggles schools face in tight times are played up.

Director Frank Coraci does a great job with the fights and the slapstick stuff, and keeps his camera on James, wherever possible.

But here’s something the movie botches. There’s too much insider stuff regarding mixed-martial arts. Faces show up, and the audience is supposed to know who these guys are. It’s a growing sport, sure. But it’s still a fringe dweller, and I wouldn’t know Mark DellaGrotte from the third string cornerback of the Buffalo Bills.

It’s corny to use them, and corny to call such cameo performers by name. But it’s necessary. And DellaGrotte has a big role, pitching in on Scott’s training.

And as “Here Comes the Boom” — that’s the song Scott wants to use as his enter-the-arena music — winds towards the ending we all see coming, the violence of all can be a bit much. Mixed-martial arts is a bloody, brutal, brawling sport; its fighters are all muscles, tattoos, shaved heads and, in the case of the guy we know Scott will have to fight (Krzysztof Soszynski), metal teeth.

But even though “Boom” doesn’t pull its punches, it’s still a lightweight genre picture, a patchwork comedy that makes good use of its biggest patch — Kevin James.