The conflict between rehabilitation and punishment is at the heart of criminal justice. In the case of young offenders, it’s especially problematic. Society’s instinct is to protect young people, but too often the response to young criminals is to label them, make them other and protect our conservative idea of the innocence of childhood. By casting them out, we offer them no way back, unless – as “Starred Up” suggests – they find it for themselves, in spite of the system. The film follows Eric (Jack O’Connell), a young offender “starred up” – that is, transferred to adult prison early. It’s a label that, for the prison’s wardens, means he is a lost cause: a violent career criminal in the making. Eric quickly begins to assert himself, proving himself against drug dealers, wing bosses… and his own father (Ben Mendelsohn). Prison gives Eric and his father Neville – a violent offender who has been locked up since his son was a child – a chance at the father-son relationship it previously denied them. Yet neither is sure how to go about playing their roles. Masculinity is, for them, synonymous with dominance, self-assertion and aggressiveness – characteristics intended to signal a lack of fear, but which actually do the opposite. Affection is weakness and love can only be tough. The path the two men take through that tangle of misplaced values is increasingly destructive, but also deeply emotional. In its own, peculiar way, “Starred Up” is quite a sweet film. As part of his maturation, Eric comes to the important realisation that his father is flawed. For all he might claim to know this at the start, there’s little doubt his father has been his model. At one point, Neville asks Oliver (Rupert Friend), his son’s therapist, to teach Eric all those things he cannot; the things he knows to be the “right” way of dealing with life, but which he is incapable of doing. Our elders aren’t just examples of how to do it right, they can also show you where the pitfalls are. That’s something both Eric and Neville come to understand and – in that realisation – are able to reconcile with themselves. Institutionalising young men is problematic. You take them out of society when they should be learning to deal with it. Few would argue that criminals do not deserve punishment, or that circumstances always forgive a crime, but the result of treating boys like adult criminals is to turn them into the men you fear they will become. Eric is a damaged young man who uses violence as a defence – but the world and the system are things against which he has been conditioned to defend himself. “Starred Up” is out on DVD now. Follow Michael Mills on Twitter.