Bullying is becoming an ever more pressing issue for schools, daycare centers, politicians and the public. Everyone agrees that bullying is a serious problem and initiatives are urgently called for to stamp it out. This Campbell systematic review studied the effects of anti‐bullying programs in schools. The conclusion is that programs generally work and bullying is reduced on average by around 20%. A total of 89 reports were of sufficient quality to be included in the systematic review. The 89 reports describe 53 different studies. However, nine studies did not provide enough data to allow the calculation of an effect size and were, therefore, not included in the final meta‐analysis. The overall analysis is therefore based on a total of 44 studies. The 44 different studies were carried out between 1983 and mid‐2009 and came from 16 different countries. The included studies were either randomized controlled trials, quasi‐randomized trials, age‐cohort studies or other controlled studies. Furthermore, the systematic review clearly states that future evaluations should measure the children's situation before and after an anti‐bullying program. This should apply to the experimental group as well as the control group to get the most accurate results possible. The authors recommend that a system of accrediting anti‐bullying programs should be developed, supervised by an international body such as the International Observatory on Violence in Schools.