All ninth graders from four Dutch s

All ninth graders from four Dutch secondary schools were invited to participate in the study. Since our aim was to study a sample of 50 adolescents, we used stratified sampling based on school class and gender to select the sample that would take part in our study (n = 90), anticipating for possible attrition rates. All students were from the higher secondary educational levels (i.e., senior general secondary education and university preparatory education), as we did not approach any students from the (lower) vocational education level. Adolescents took part in our study voluntarily. Informed consent was obtained from all individual participants and their parents before participation.