Inclusive and supportive classroom environments are essential, particularly during political and societal crises such as wars, disinformation, polarization, and rising populism and extremism. While existing research underscores the importance of such environments, few studies comprehensively examine the impact of anti-hate speech prevention programs on classroom dynamics and students' social development. This study addressed this gap by investigating the direct and indirect effects of the HateLess anti-hate speech prevention program on inclusive classroom climate, classroom cohesion, empathy, and self-efficacy among adolescents. A sample of 820 adolescents aged 12 to 16 years (M = 13.27, SD = 1.04) from 11 German schools was divided into an intervention group (n = 567), who participated in the 1-week program, and a control group (n = 253). Multilevel mediation analyses revealed that, at T2 (1 month after the intervention), the intervention group reported significantly higher levels of inclusive classroom climate, cohesion, empathy, and self-efficacy than the control group. In addition, inclusive classroom climate and cohesion were positively associated with empathy and self-efficacy, and significant indirect effects indicated that the intervention's impact on empathy and self-efficacy was partially mediated through classroom climate and cohesion. These findings highlight the effectiveness of HateLess in fostering inclusive classroom environments and suggest integrating such interventions into school curricula to cultivate supportive learning spaces that empower adolescents to address hate speech effectively.
Keywords: adolescents; empathy; hate speech; inclusion; prevention; school climate; self-efficacy.