Table 1 The student questionnaire

The questionnaire consisted of the following different sections:

General information, that is, gender, age, nationality, school institution, and class attended;

 • Five questions about the area of verbal bullying (e.g. being called an offensive nickname);

 • Five questions about the area of physical bullying (e.g. being attacked);

 • Five questions about the area of indirect bullying (e.g. being ignored or secluded);

 • Five questions about the area of resilience (e.g. talking to someone about having been bullied);

 • Five questions about the role of observers (e.g. seeing a classmate being teased and not intervening);

An open-ended final questionnaire section to freely express thoughts about 1) the content of the questionnaire and 2) bullying in general.

The analysis was constructed as follows:

For each answer, a score between one (never) and five (very often) was assigned. The score was then used to detect the baseline level of bullying with the following three methods:

1. Sentinel questions, where the presence or absence of bullying was investigated through yes/no answers to the most significant questions in an area. The responses very often, often, and occasionally were considered affirmative answers.

2. The five-question method, which considered bullying to be present whenever the student answers yes (i.e. occasionally, often, or very often) to at least one of the items in the survey area.

3. The score of seven method, where the answers to each question were scored and added and the presence or absence of bullying was then determined, where the value of seven was considered the cutoff (i.e. the respondent could answer occasionally at least to at least one of the questions in an area).

Both the pre- and post-intervention questionnaires were identical. The only the difference was that the pre-intervention questionnaire investigated an interval period of ‘the last three months’, whereas the reference time frame in the post-intervention questionnaire also included the previous six months, before the summer break.