Each year in Britain, we lock up 2,000 school-age children. Vinney Green Secure Unit locks up some of the youngest and the most troubled; the kids no one else can manage - whether they are a danger to each other, or a danger to themselves. Filmed over a year, with unprecedented access to the unit, the children and the staff who care for them, this extraordinary series tells their stories and finds out what's being done to set them straight. It documents the journeys of boys and girls who are behind bars, and follows the daily life at Vinney Green as the staff try to change them.Vinney Green houses 24 children aged from 10 to 17. Some have committed very serious crimes. Others began getting into trouble when they were at primary school. Some are sent here for their own protection. And for some, simply the chaos of their lives has led them down the wrong path. For most this is their last chance - and an opportunity to change. In their own words, they explain what it's like to be locked up while you're still a child.Acts of violence committed by girls have doubled in the last four years. This second film follows three girls who are in Vinney Green for a variety of reasons, including violence to others. Some are there because they are hurting themselves so badly that they have to be locked up for their own protection. Jess has a violent past: 'I'm just an angry person', and the staff have got their work cut out to try and control her. Ruby has run wild and is kicking against the unit's strict regime: 'They always have the last word and I don't like it.' And Steph is there for her own protection: 'It's the safest I've ever felt.' Over a tempestuous summer, we look at whether the unit can tame them.