Bullying is a form of school violence. According to an agreed international definition, bullying is characterised by aggressive behaviour that involves unwanted, negative actions and an imbalance of power or strength between the perpetrator or perpetrators and the victim. Unlike isolated incidents of school violence, bullying is also characterised by repetition over time. The number of repetitions may vary and, for example, major surveys that collect data on bullying measure the frequency of bullying in different ways. The international Sustainable Development Goal Thematic Indicator 4.a.2 that measures the ‘percentage of students who experienced bullying during the past 12 months, by sex’, which was adopted in 2018, defines that the frequency of aggressions should be at least once or twice a month or more for a student to be considered a victim of bullying.
It is important to note that here is no standard definition of bullying across the six international surveys that collect data on the prevalence of bullying. Some of them do not even provide a definition. These surveys are the following: