A return to horror from buddy comedy duo Simon Pegg and Nick Frost should be cause for major excitement in the genre community, as Shaun of the Dead is still the zombie-comedy all zombie-comedies are compared to, and even The World’s End worked as a funny and thrilling sci-fi comedy about alcoholism and growing up. So to see them return for a film that combines Harry Potter with subterranean monsters ala Tremors should be reason enough for celebration. If only Slaughterhouse Rulez was as good as the promise of that cast.

Finn Cole plays Donald ‘Ducky’ Wallace, a kid who caught a lucky break and got admitted to the very exclusive elite boarding school, Slaughterhouse. This is a place that groomed past prime ministers, and such famous names as the Marquis de Sade, Jack the Ripper, and Piers Morgan, so expectations for new students are a bit high. Hundreds of years old, the school is full of tradition that will offer stateside viewers constant reminders of the wizarding world of Harry Potter; students are divided into houses, one for the athletic jocks, one for the smarty pants, and there’s even a version of Hufflepuff where the rest of the students are. Sure, this may be a coincidence, but when you have the school’s Headmaster, played by Michael Sheen, warn students that going to the woods near the school is forbidden with a quote that is almost word for word what Dumbledore warns his students (“Stay off the woods unless you wish to suffer a painful death”), then you have the audience raising eyebrows. Add in a rich, entitled bully with white blond hair and you are halfway to Hogwartz.

The first hour of the film is mostly spent on school drama/mystery, exploring the different characters and how messed up the boarding school system is, and there’s quite a lot going on. Ducky is trying to fit in at the school, struggling to make sense of all the rules and established groups that exist within the vast grounds of Slaughterhouse. Ducky realizes he’s broken some unspoken rule by flirting with posh girl with a heart of gold, Clemsie (Hermione Corfield), and is busy figuring out what happened to the gay viscount that hanged himself with his school tie in the room Ducky now inhabits. Everyone but the dead kid’s best friend and roommate Willoughby Blake (Asa Butterfield) is trying to forget about the tragedy, and there are hints that Blake is either trying to get some revenge on the sadistic bully Clegg (Tom Rhys Harries) or is about to off himself too.

Oh, and have I mentioned Simon Pegg’s house master who is named Meredith Houseman (seriously) and his complete obliviousness to being dumped by out-of-his-league Australian girlfriend (Margot Robbie, continuing from where Cate Blanchett left off in Hot Fuzz), or Nick Frost’s role as a former student turned eco-protestor and drug-dealer living in the school’s forest. The pair are as funny and likeable as ever, even if they don’t cross paths but for a minute. Frost is important because he’s worried about the school’s Headmaster allowing fracking on the woods and the environmental impact it will have. This is the theme at the center of the film, and the three credited writers, Crispian Mills, Henry Fitzherbert and Luke Passmore waste no time in having every character in the film mention the dangers of fracking and how irresponsible it is.

If it sounds like I’ve written a lot without even mentioning the monsters or the horror, it’s because Slaughterhouse Rulez takes its sweet time before finally introducing us to the underground creatures that will wreak havoc in the school at the 1-hour mark. This is when the film switches gears and goes full horror-comedy, as well as earn its mostly unnecessary R-rating. While lots of people complain when a horror movie gets a PG-13 rating, not many do the same when a film that could have easily been marketed to teenagers gets pushed to an R-rating for no reason. There isn’t much gore here, with quite a few kills being pushed to just off-camera, and it feels like they added just enough swear words in ADR to justify the rating. Then there’s the Edgar Wright-style editing, which feels like a cheap imitation instead of respectful inspiration; it all makes you wish you could see what a better writer-director could do with this story.

Otherwise, the last half-hour of the film is the kind of creature-feature fun we deserved all along. The giant dog-slug monsters are brought to life with practical effects, helping them look real, and they’re aided by decent action. There are drone shots that help visualize the massive school grounds that become a battleground, green flames caused by the fracking-related toxic gases giving a nice and ominous aesthetic to the set, and the final battle against a nest of creatures is pleasantly slapstick and gory.

Slaughterhouse Rulez starts with plenty of potential for a fun and slapstick horror-comedy set in the bizarre and posh world of elite British elite boarding schools, but a heavy-handed political message, a glacial pace, and a lack of both horror and comedy prevents this one from actually ruling.

Slaughterhouse Rulez is now available on UK Blu-ray.