When Charlie Day and Richie Keen, star and director of the raunchy comedy “Fist Fight,’’ were flying into Boston Sunday night to promote the movie, they, like much of New England, were worried. The New England Patriots were down 28-3 in the Super Bowl and time was running out.

“First of all, I’m from Rhode Island, and I’m a New England fan,’’ recalls Day, whose cult hit series “It’s Always Sunny in Philadelphia’’ just started its 12th season on FXX. “But quite selfishly I thought, I don’t want [the Patriots] to lose and then go to Boston when they all feel terrible and have to talk to them about the movie. But when we landed we asked the guy who drove us to turn on the radio just as they were making the big turnover. And we made it to the hotel just in time to see the most incredible fourth quarter in the history of football.’’

Perhaps the Patriots’ victory is a good omen for the fortunes of their film, which opens Friday. “Fist Fight’’ takes place in a high school with a football team whose “tradition is losing.’’ But that’s the least of the school’s problems. The students are out of control, the school is underfunded, the teachers are demoralized, and many are about to be laid off. It’s the last day of class, a traditional saturnalia where students prank the faculty and staff, so obscene drawings are everywhere, paint bombs explode, and a horse is wandering through the halls.

And it is the worst day in the life of Day’s character. He plays Andy Campbell, a mild-mannered English teacher who for reasons best explained by the movie has to engage in the title bout after school with the ferocious Mr. Strickland, a history teacher feared by all and played by the formidable Ice Cube.

“These students could probably use a winning football team to get the aggression out,’’ muses Keen, a frequent director of episodes of “It’s Always Sunny in Philadelphia,’’ making his feature debut. “Those are some terrible kids.’’

“It’s certainly not my school, because it was run by monks [Portsmouth Abbey] and you’d get expelled if you were as volatile as this,’’ says Day. “But Richie and I did look up on places like YouTube a lot of high school pranks students were playing and pretty much every one in the movie comes from something we found kids had done in their school. Like the mariachi band following the principal around all day. Disassembling a car and reassembling it. We found some of the most wonderfully decorated principal’s cars on line. There was even one shot of a cat someone had drawn on the blackboard and when you erased it — but I don’t think you can use that in a family newspaper.’’

Despite the raunch and outrageous black comedy familiar to fans of Day’s show and his two “Horrible Bosses’’ movies, Day and Keen insist that the film is trying to make some serious points.

“The challenge was how do we make a movie about a fight that’s not just a big guy beating up a wimpy small guy,’’ says Keen. “How do we make it about a cathartic experience the school is having on the last day of classes when almost every teacher is getting downsized. And the way Charlie’s character handles what’s happening in the school versus the way Ice Cube’s character handles it is completely different.’’

“We put in some things about accountability,’’ adds Day. “Like Ice Cube’s character saying kids get a trophy these days just for participating, which is something that resonates with people. Certainly the answer is not extreme violence, but people do feel somewhat handcuffed today with political correctness. So I think those themes help us tell a story which is not just about a bully.’’

“We also try to hit on bullying as well,’’ says Keen, “how do you stand up to a bully. Like me: I was sort of like Charlie’s character growing up. I got bullied and picked on and in some ways this was like my fantasy what would happen if I actually eventually stood up to the bully.’’

“If there’s a piece of Andy Campbell that’s a little bit like me,’’ says Day, who is a wiry 5 feet 7 inches, “I always stood up to bullies. The character as we set him up in the beginning is a real softie. But he realizes that he can’t run anymore and he has to stand his ground and survives and I think he gains some strength in that.’’

So Day himself has had experience in fist fights like the one in the movie?

“Any time someone tried to bully me,’’ he says, “I shot right back with a wiseacre remark or I fought back. I was a scrappy New England kid. A dirty fighter. I hit a kid with a trombone once. I was in the band. I just happened to have a trombone with me and hit him in the knee.’’

“That’s a cool move,’’ says Keen, impressed. “We could have used it in the movie.’’

Peter Keough can be reached at petervkeough@gmail.com.