But by the end of the film, it’s just so hilarious that its flaws can be forgiven.

The film pits It’s Always Sunny in Philadelphia’s Charlie Day against comedic action man Ice Cube (21 Jump Street, Ride Along) in the teacher tiff to end all teacher tiffs.

The pair work at a disadvantaged high school on the last day of the school year – prank day.

Day is the not-fully-committed, straight-laced English teacher Andy Campbell.

He is happy enough to let the students run riot but doesn’t actively want any harm to come to them.

His primary concern is keeping his job in the the midst of staff cuts so he can provide for his soon-to-be-born second child.

Ice Cube plays Strickland, the tough as nails disciplinarian who is willing to set a student straight with the threat of a baseball bat.

The history teacher has no time for pranks and will not abide being made a fool of.

The two teachers’ fates become intertwined when a student prank gets out of hand in class and the pair are called to the principal’s office.

Campbell has the chance to stay tight-lipped about a questionable decision Strickland makes, but instead rats him out.

The battle lines are drawn and the promise of a #teacherfight is set.

This first portion of the film – the set-up – is pretty stock-standard for a crass film.

But it’s after the fight threat that things get really interesting.

Campbell’s attempts to get out of the fight grow increasingly outrageous and ridiculous.

Soon enough the audience can forget how dumb most of the humour has been and just roll with gags.

Ice Cube is always on point and at his angry best.

Day though is shouty, and shouting on its own is not enough to deliver the laughs.

The supporting cast also play their parts.

Tracy Morgan (30 Rock) is a little underwhelming as the gym teacher by Jillian Bell (22 Jump Street) is a revelation and consistently steals every scene she’s in as a meth-addicted teacher of questionable morals.

Check your brain at the door and you’re in for a treat.