Several large evaluation studies have pointed at the Olweus model as the most successful for preventing and reducing bullying in schools.
In 2008 Elisabeth Ttofi, David Farrington and Anna Baldry published a comprehensive metastudy upon request from the swedish council of violence prevention. This study - Effectiveness of Programmes to Reduce School Bullying - conclude first and foremost that school based anti-bullying programs work. Six out of the ten most successful school based interventions were based upon Dan Olweus' program for bullying prevention.
The report from the study, supported by the Swedish National Council for Crime Prevention