Esther Mertens

40 | Chapter 2 Parents might feel disengaged from the study and do not complete the questionnaire. We try to minimize this possible threat by emphasizing the importance of it. Furthermore, both consent and the questionnaire are digital. Parents do not have to actively return a consent letter and can complete the questionnaire at home at a time convenient for them. In addition, we will send reminders for completing the questionnaire to parents through the school’s parental communication system. Moreover, we will organize a raffle to motivate the parents to participate. Teachers might not have enough time to complete the questionnaires during work hours. They have to fill in a questionnaire for each student which takes up a lot of time. We try to reduce this possible threat by asking multiple teachers per school to complete the questionnaires. Multiple teachers can decrease the burden of the questionnaires since they only have to complete the questionnaires for a subgroup of students (e.g., one class). Additionally, we have personal contact with the teachers completing the questionnaires. This enables us to directly approach a teacher from whom we have missing data. Another possible threat is insufficient or low treatment adherence. Teachers might deviate from the manual or are not able to complete a lesson due to limited time. We try to gain insight in the quality of implementation by asking questions about treatment adherence every three lessons and by observations during a subsample of R&W lessons. This information can be taken into account in the analyses. The current study offers the opportunity to examine whether the broadly implemented intervention R&W is effective in positively stimulating the socio- emotional adjustment and social safety of prevocational students. Furthermore, a deeper understanding of the intervention can be gained by studying moderators and mediators. When proven effective, the implementation of R&W in prevocational schools can be stimulated. Additionally, possible adjustments to increase the effectiveness of the intervention for certain subgroups (i.e., students characteristics) might be identified.