Actor Charlie Day (“It’s Always Sunny in Philadelphia,” “Horrible Bosses”) stars in his first leading role in the upcoming comedy film, “Fist Fight,” starring Ice Cube, Tracy Morgan, Dean Norris and Jillian Bell.

A loose remake of the 1987 teen comedy “Three O’Clock High,” “Fist Fight” follows high school teacher Andy Campbell (Day) who is challenged to an after school fist fight after accidentally getting his colleague Ron Strickland (played by Ice Cube) fired.  Taking place on the senior-prank-filled last day of school, Campbell tries desperately to not only avoid being fired but also evade a fight he’s destined to lose.

Television director Richie Keen, also from “It’s Always Sunny in Philadelphia,” directs his first feature film with “Fist Fight” and takes control of a full cast of comedian veterans and newcomers.

The DePaulia recently sat down with Day and Keen of “Fist Fight” to discuss past high school pranks, and filming a fight scene with Ice Cube.

Your character on “Always Sunny” is illiterate, barely had a job, ate cat food but then here you’re this family man English teacher.  What was the transition like, did you draw anything from your “Sunny” character Charlie Kelly?

Charlie Day: No! I was relieved to be a character that could read and write, relieved to play someone mannered a little more like myself in many ways but then when he unravels he dips into more of Charlie Kelly hysteria and psychosis.    

Richie Keen: I feel like we did a really good job in casting because you see Charlie not be the craziest person in the room. You have Jillian Bell, Tracy Morgan and Kumail Nanjiani, but it’s Charlie who is like “Hold on, let’s think about this.” So that was really fun to see something different.

With all these comedians co-stars from Jillian Bell and Tracy Morgan, how much of the film was improved?

Keen: The answer is, there was a lot of improv but the question is how much did we actually keep. We felt like we’d be fools not to let everyone do some improv, so we shoot everything that was scripted, but there was no way I’m going to let Charlie and Kumail stand together and not let them mess around for an hour.

And if they do that improvisation and someone breaks but it’s funny enough, do you just do it again?

Day: That’s right so you improv or do an alt (version of the script) and people laugh, but you know that’s really funny, we have to do it again. I feel like it’s never quite good as that first take.  That first take, whatever magic is in there, is lost.  That’s why you have to try your hardest not to laugh.

Keen: Of course he’s saying this!

Day: Oh I know, because I’m the worst at it.

Keen: Some of my favorite moments on set is watching Charlie just barely not break, like you can see his lip starting to curl.  But it’s a testament to the cast that would just hang out in between scenes, I can picture Tracy Morgan walking around in a tank top just telling stories.  It shows on screen, everyone’s having fun on set.

This film obviously focuses on teachers and high school, so I was wondering what you guys were like back in high school as students? If you did any senior pranks?

Day: I was too scared to get expelled. My sister went to the local public school, my parents thought maybe I had some potential so they had me apply to this fancy public school, and I got in.  We were nickel-and-diming our way to that school so I knew if I got expelled, I’d be a huge disappointment.  But I was terrible in school, I was a jokester and couldn’t pay attention because I was distracted by all the girls and fantasizing about playing professional baseball.

This is high school to the extreme, with horses for senior pranks, fights with Ice Cube and a dance routine with Big Sean, what was the hardest scene to film for you?

Day: Truth is, sitting in this chair right now, I’m still having to adjust because of the pain from this movie — and it’s been a year and a half since we filmed it.  Without question, filming that fight was the most difficult thing as an actor I’ve had to physically.

This film touches upon the issues behind the U.S. school system, what did you want viewers to take from the film?

Day: I always hoped that people laughed but they don’t feel as if their laughs came cheap.  You had good laughs but you’re also thinking about the school system and what teachers are going through. I’m not hoping to change the world but that you leave with both things.