This US documentary on bullying arrives on the back of a Stateside ratings furore that led to it initially being released unrated after censors absurdly classified it “R” on language grounds. That rating (later softened after cuts) would have prevented under-17-year-olds from seeing the film in cinemas – precisely the audience that should be exposed to this moving and sometimes enraging film about entrenched behaviours that virtually everyone will recognise from their own school days, whether as former victims, perpetrators or both.

That the film is set in the US Bible Belt is bitterly ironic given the determinedly non-Christian behaviour it depicts, habitually accepted as “just one of those things that are hard to police” by complacent school staff. Director Lee Hirsch divides the running time between the parents of two teenage suicide victims, a handful of children still being bullied, the views of their school officials, and an incendiary public meeting.

The bullying – both verbal ostracism and physical violence – focuses on any kid seen by their peers as weak or different, whether they be a tomboyish lesbian or a sensitive introvert with an unusual face. There are some powerful moments here in a film that will give many...