“…It was possible to develop hypotheses about whether separate components, in general, would work better for some. We expected that (1) children below 12 years benefited more from school-based antibullying intervention components than those above 12 years, based on research that showed that anti-bullying interventions become less effective from grade eight onwards and may then even induce iatrogenic effects, possibly because current anti-bullying interventions do not meet adolescencespecific needs for status and respect (Yeager et al, 2015(Yeager et al, , 2018; (2) boys benefited more from school-based antibullying intervention components than girls, as research has shown that interventions may gravitate towards visible, more explicit-typically male-bullying (Barbero et al, 2012;Volk et al, 2012); (3) school-based anti-bullying interventions are more effective for ethnic majority than minority youth, because interventions generally do not attend to ethnicityrelated issues, such as race and ethnicity-based stereotype harassment (Peguero & Williams, 2013;Vervoort et al, 2010;Yeager et al, 2015); (4) youth with higher socioeconomic status (SES) benefited more from school-based antibullying interventions than youth with lower SES, as lower SES youth may need a relatively intense intervention since they might be more likely to engage in bullying or to become victimized, although this might be different across countries (Hosozawa et al, 2021;Tippett & Wolke, 2014); and (5) youth who bully or who are victimized prior to intervention benefited more from school-based anti-bullying interventions, based on research that showed intervention effects to be larger for those victimized or bullied before the intervention (e.g., Ferguson et al, 2007;Juvonen et al, 2016-for an exception, see Kaufman et al, 2018). This suggests that interventions are more relevant and engaging for youth with more severe problems, who may also have more room for behavior change.…”