Critical response
Despite poor ratings, overall reception from critics for the series was mostly positive. It received praise for its darker tone, writing, themes, and acting, as well as for the overall evolution of the characters during the series; Katherine Kelly and her character Miss Quill, in particular, were singled out. However, the Shadow Kin were considered weak enemies, and the first episodes and finale were criticized for their fast pacing. Reviewers noted that the show was similar to Buffy the Vampire Slayer, with some critics considering it a quality that made it stand out more from Doctor Who, and others being critical of it. Review aggregator website Rotten Tomatoes gives the series an 82% rating based on 17 reviews, with an average rating of 6.9/10.
GamesRadar+ called Class "really, really good. So good, in fact, that even after only two-thirds of its very first season, it’s possible to see the show’s potential bubbling over the sides like an over boiled pot of pasta." Doctor Who TV called Class "a remarkably efficient, seldom-rushed, eight-episode series". Despite being critical of early episodes, IndieWire gave the series as a whole a positive review, stating "while the show knows how to juggle the heavier issues and high-concept scenarios, it doesn’t skimp on the fun." They highly praised Kelly's performance, calling her "fabulous", and the characters of Miss Quill and Matteusz, considering them "absolute scene stealers".
Collider was positive about the series, praising the character of Miss Quill, whom they called "the most consistently delightful part of this series", the fact that the character's adventures were "not easy or without its considerable cost", and its themes of loss and grief, stating "Class is at its best when it slows down and doubles down on the more grounded, relatable struggles of its characters. As is the case with good teen horror dramas that has come before it, Class' scariest, most interesting villains aren’t alien monsters that wipe out entire civilizations, but rather the real-world problems like losing a parent, a girlfriend, or losing the time and space to simply be a kid." However, they criticized the show for being too different from Doctor Who, stating "If you’re looking for more of the science fiction idealism that Doctor Who tends to provide, stick to the new season. Here be dragons (sometimes literally) and they will unceremoniously kill people."
The A.V. Club gave a show a B rating, particularly praising the "winning cast of incredibly talented young British actors and its casual diversity, which many contemporary teen shows strive for, but which few pull off so effortlessly." They highly praised the show's representation of homosexual characters, "presented with a refreshing matter-of-factness, not a self-congratulatory pat on the back", the performances (especially Kelly's whom they called a "scene-stealer"), and the characters, stating "There’s not a weak link among the uniformly excellent ensemble and the show serves its teenage characters particularly well by allowing them to have an emotional intelligence that’s not always granted to young protagonists. [...] The most successful parts of the series explore the ways the students support one another through all the weighty challenges they’re faced with, both of the real-world and sci-fi variety. And it weaves in just enough comedy to keep things from becoming too maudlin or too bleak." However, they felt that the science-fiction elements of the series felt out of place: "the extensive exposition needed to introduce the show’s ever-growing mythology starts to sound like someone perpetually reading out the rules for an increasingly complicated adventure board game. As quickly as one element is introduced, more complications are thrown on top of it, leaving the series with little room to breathe."
Entertainment Weekly gave the show a B rating, highly praising the cast: "The young actors are all very talented and have no trouble handling the show’s heavier material. In fact, I found myself wishing there had been more than just eight episodes in the first season because it would’ve been nice to have seen a bit more of the group’s lighthearted side. That being said, the show’s MVP is clearly Kelly, whose Quill not only delivers some of the best lines but also the best arc of the season. Without giving too much away, her dynamic with one of the student leads is the source of some of the season’s most interesting thematic material." However, they regretted that the show's darker tone made it "slightly less fun" than Doctor Who. The Los Angeles Times gave the series a mixed review, stating that Ness' storytelling felt "muddled and mechanical" and "tells you too much, too fast." They however praised that "the female roles are especially strong and well played", particularly praising the performances of Kelly, Sophie Hopkins and Vivian Oparah.
In a post-cancellation review of the series, Morgan Jeffrey of Digital Spy debated the reasons the series was unsuccessful in finding an audience, called the show "the spin-off no-one asked for", and argued that the reason it failed in ratings was due to the BBC not knowing who the show was for: "A teen-oriented drama with adult themes, spun off from a series intended (primarily) for children, the tone of Class was every bit as confused as that muddled origin would suggest." However, and despite having given the show's premiere a mixed review, he stated that "Class wasn't a total write-off. Far from it. The show absolutely had its gripping moments, its standout episodes (the poignant "Nightvisiting" was a clear highlight) – and, oh, what a cast. They'll all be going on to greater things. Most of its problems could've been fixed, if it had done well enough to secure a second series."
