Sweden will start jailing children as young as 13 from July 1 this year. Not in juvenile homes or special facilities - in actual prisons, with iron bars, metal doors and locked wings. The Rosersberg prison near Stockholm is the first facility prepared for the purpose.

Rosersberg will house up to five minors per wing, across four separate sections. The cells are presented as „rooms in a student dorm" - with a desk, a bookshelf and a TV. But the door is heavy, metal, with a keypad that locks from the outside. A cell that looks like a student room is still not a student room.

Even the Swedish Prison and Probation Service opposed the law. The director of Rosersberg, Gabriel Wessman, doesn't hide it: „Every person who walks into a prison is first and foremost - and above all - a failure of many institutions before us." That is the kind of sentence a director writes about something happening by state decision. His own views weren't in line with the policy, but he has to implement it.

The daily schedule in this prison for children looks like this: 11 hours a day locked in a cell. Restricted phone access - and only via analogue handsets, to numbers approved in advance. Education continues, but in locked classrooms with restricted internet access. For a 13-year-old boy, that is a psychological experiment almost no developmental psychology would recommend.

The prison sentence applies only to the most serious crimes - murder, rape, explosive attacks. But in many countries the scope of „most serious crimes" expands every year, and there is no guarantee Sweden will hold to its initial limits. The center-right coalition lowered the age of criminal responsibility from 15 to 13 to close a loophole that organised crime groups had been exploiting when recruiting minors.

Higher recidivism rates in traditional juvenile homes were the main public justification. But a 14-year-old released from prison reoffends roughly as often as a 14-year-old released from a juvenile home - that's what the research shows, and that's what the government has no answer to. Sweden is now running an experiment in front of the whole world. The Balkans are watching closely - several countries in the region are already talking about lowering the age of criminal responsibility, and Sweden will be the model that either emboldens them or warns them off.