A quasi-experimental study with ninth graders evaluated a 1.5-hour hate speech teaching unit in an intervention vs. control group (N = 82) before (T1) and after the intervention (T2). Participants reported frequency of witnessing hate speech (T1), hate speech norm and self-efficacy countering hate speech (T1 and T2), and knowledge concerning hate speech (T2). Repeated ANOVAs showed a significant three-way interaction for hate speech norm: Especially among those who witnessed hate speech more often, the program diminished the agreement to hate speech norm. Self-efficacy did not change significantly, but knowledge was slightly higher in the intervention group, particularly among students with a migration background. In sum, the intervention showed effects on norms and knowledge, and longer programs with more interactive elements for coping with hate speech seem recommendable. The current research is a first step and evidence-based practice for prevention of hate speech like the current evaluation study is desperately needed.