Sex Education season four review: For all its vibrant, saturated palate, this has always been a show rendered in black and white

The most American television series ever to be set in Britain draws to a close on Netflix

Those who can’t do, teach. And those who can’t shag, start running sex therapy clinics. That has always been the essential premise of Netflix’s Sex Education. Over the course of three series, kids have fallen in and out of love, in and out of popularity, and in and out of each other’s beds. All while dispensing preternaturally mature advice about sex and relationships. Now in its fourth and final season, the show is ready to see its characters fly the coop, finally leaving behind the cloying world of high school.

It’s about time too, as the plausibility of these characters as school-age minors approaches breaking point. Otis (26-year-old Asa Butterfield) has finally landed Maeve (27-year-old Emma Mackey), the impossibly cool, talented and beautiful girl he’s spent a trilogy of seasons pining over. But their stars aligning was just in time for her to shoot off to America on a special student programme, led by Schitt’s Creek’s Dan Levy. Back home, Eric (30-year-old Ncuti Gatwa) is still struggling to live an authentic life as a young gay man while satisfying the demands of his religious family, while Aimee (29-year-old Aimee Lou Wood), recovering from the trauma of sexual assault, finds an unexpected connection. Meanwhile, defenestrated headmaster Mr Groff (Alistair Petrie) tries to heal both himself and his relationship with troubled son Adam (26-year-old Connor Swindells), and Gillian Anderson’s Jean is struggling to balance co-parenting with hosting a new radio show. And… breathe.

Perhaps the biggest change is that the action has moved from Moordale Secondary School to Cavendish College. For those who have found the show too “woke” up to now, Cavendish will be a brutal immersion therapy. “My God,” gasps Eric, beholding a campus almost technicolour in its diversity, “all the gays, everywhere.” The show collides the brittle, spiky characters from Moordale with a pastiche of the inclusion agenda – with mixed results. Sex Education has always been unapologetically preachy, and many of the excesses that it lampoons it also, tacitly, promotes. “Just an ally coming through,” Ruby (25-year-old Mimi Keene) announces cynically, as she tries to climb up the new social hierarchy, but ultimately allyship is crucial both to the show’s manifesto and that character’s interpersonal success.

For all its vibrant, saturated palate, Sex Education is a show rendered in black and white. In any given scenario – whether it’s an accidental outing, gossiping non-gossipers, or a procession of characters putting relationships ahead of friendships – the black-and-white lines are firmly drawn. The fact that each character is capable of being wrong as well as right gives the illusion of grey, but rarely is there any true ambiguity. That combination of the overwrought drama of The OC or Beverly Hills, 90210 and the wry British humour of The Inbetweeners or Gavin and Stacey has always been the key to its blockbuster reception. It is, potentially, the most American television show ever to be set in Britain.

Many romantic comedy TV shows face a struggle once the “endgame” begins. Two characters who seem destined for one another, finally hooking up – that tends to suck the air out of proceedings (think Jim and Pam in the US version of The Office, Luke and Lorelai in Gilmore Girls, or even Ross and Rachel in Friends). And Sex Education has always been heading towards the climax of Otis and Maeve consummating their desire. But let’s face it: the endgame doesn’t often arrive when you’re 17, and the lure of America brings a third point to their triangle. “I love it so much out there,” Maeve tells Otis. “I feel like the best version of me.” For all that the show’s ethics have been painted in stark, black-and-white, as the book closes, suddenly there’s a splash of grey.

The triumph of Sex Education has been making didacticism appealing. There are few shows that have pulled off a sermonising tone with such panache. The quality of the acting, writing and production put the series firmly in the middle of the televisual pack, but as a progressive voice it has been all but peerless. Despite the tendency towards a moral binary, when the climax of this sex saga is finally reached, the story embraces the uncertainty of the morning after.