Assessment Procedures
A team of four local interviewers was trained in data collection in a 4-day workshop. Standardized procedures were developed to ensure objectivity and reliability. A pilot study at one primary school (not included in this study) was conducted to ensure the feasibility of the questionnaire administration. All assessors underwent supervised training in assessment procedures during the pilot study and conducted a supervised assessment in the first week of this study’s assessments. Daily team meetings and exchanges between the assessors and the research team ensured high-quality data assessment. In addition, quality checks were conducted by way of random supervised assessments. All questionnaires were administered in Swahili language. The measures that were not available in Swahili were translated following established international guidelines (Brislin et al., Students were selected from the fifth and sixth grades due to appropriate literacy levels and ability to comprehend the questionnaire items, as well as availability during the follow-up assessment. To seek parental consent for the students, a letter explaining the study aims and procedures was sent together with informed consent forms to the students’ parents. The students who provided informed consent forms signed by their parents and themselves filled out questionnaires in groups of one to three students on the school grounds under the supervision and guidance of a research assistant (i.e., the assessor read out the questions and answer options and explained them, if necessary, and the students selected the answer options and marked them appropriately). The seating arrangement ensured sufficient privacy to minimize social-desirability bias. The completion of the guided questionnaire assessments took 40 min on average.