Assessment of the Prevalence of Bullying and Its Effects on the Mental Health of Junior Secondary School Students in Rivers State

School bullying has emerged as a widespread phenomenon in Nigerian secondary schools, with documented negative effects on victims' psychological wellbeing and academic engagement. This study assessed the prevalence of bullying and its relationship with mental health outcomes among Junior Secondary School students in Port Harcourt, Rivers State, South South Nigeria. A descriptive survey design was employed, with 300 JSS1 to JSS3 students from eight schools in Port Harcourt Municipal and Obio-Akpor LGAs completing a validated Peer Victimisation Scale and the General Health Questionnaire-12. Stratified random sampling was applied. Results revealed that 53.7 percent of respondents had experienced at least one form of bullying in the preceding school term. Physical bullying was most prevalent (61.2 percent of bullied students), followed by verbal bullying (74.8 percent) and relational exclusion (44.4 percent). Cyberbullying was reported by 28.3 percent of students, higher among urban school students. Bullying victimisation was significantly associated with elevated psychological distress on GHQ-12 scores (p < 0.001), poor school attendance (p < 0.01), and lower academic self-concept (p < 0.01). Victims were significantly less likely to have disclosed bullying to an adult (18.2 percent versus 0 percent for non-victims). The study concludes that bullying is prevalent and psychologically harmful in Port Harcourt secondary schools. Recommendations include anti-bullying school policies, counsellor-facilitated reporting systems, teacher training on bullying recognition, and peer support group establishment. Keywords: school bullying, mental health, junior secondary students, Rivers State, peer victimisation