2.2. Sample
SECONDARY
All Norwegian-speaking students starting the first year of upper secondary school in the 16 included schools were invited to participate. Those under the age of 16 years needed their parental or guardian consent to participate. Among the 820 students who needed consent, 72% provided feedback, and 70% gave content for the student to participate. A total of 2203 students from either a general or a vocational study track responded to the baseline survey (at the start of the first school year). Of the 2203 pupils, 1884 responded to the first follow-up survey (in the spring of year 1), 1287 pupils to the second (spring of year 2), and 756 pupils to the third (spring of year 3). The number of survey respondents decreased over time from the start to the end of year 3. Among other reasons, this was because students who attend a vocational education program are most often in apprenticeships after two years of upper secondary school. The students from vocational subjects, who were not present at the schools in the third year, were contacted via SMS and prompted to complete the survey online. However, very few responded. We also found that at the final measurement point, fewer students responded to the survey than were registered in each class. Moreover, at this time, fewer students who had not been present at the data collection time subsequently responded.