THE STORY: Clint Hadson (Elijah Wood) is a struggling writer who returns to his old elementary school in Chicken, Illinois, as a substitute teacher. His high school crush, Lucy McCormick (Alison Pill), is teaching there too, but she is dating the boorish physical education teacher, Wade Johnson (Rainn Wilson). Meanwhile, the children start to exhibit terrifying behaviour as an infection spreads rapidly through the school.

The recent Scouts Guide To The Zombie Apocalypse crossed the zombie flick with the teenage sex comedy to middling effect. The more successful hybrid is Cooties because it energises the genre by juvenilising it.

If you have always had the sneaky suspicion that children are little monsters, well, this movie is firmly on your side. It smartly blurs the line between pint-sized terror and flesh-eating hellion because really, who can tell sometimes when it comes to kids?

And so we get this macabre scene of an infected child taking a bite out of another pupil - and it does not strike the substitute teacher as anything out of the ordinary.

Kudos to the debut directors Jonathan Milott and Cary Murnion, as well as writers Leigh Whannell (Saw, 2004) and Ian Brennan (co-creator of horror comedy television series Scream Queens, 2015), for not handling the subject matter with kid gloves.

They pull no punches with the gore and violence in the scenes of carnage on the playground, even showing the kids playing with detached eyeballs and substituting human intestines for a skip rope.

There is a generous serving of humour as well, from the oddball characters to the droll dialogue. When things start spinning out of control, Wade exclaims: "You can't eat the teachers, man."

It would be tempting to write off Wood for slumming it after the blockbuster success of The Lord Of The Rings movies by making smaller, quirky movies. That would be doing him - and the offbeat charms of films such as Cooties and mystery thriller Grand Piano (2013) - a grave disservice.