The study sought to establish the causes, manifestation and impact of classroom aggression on students’ physical and mental health and academic performance in Harare urban secondary schools in Zimbabwe. A qualitative research design methodology was used in this study. The participants in the study were 40 students and 15 teachers from 10 urban schools in Harare Metropolitan Province. In-depth interview schedules and focus group discussions were used to collect data. The study used a narrative analysis of interview and focus group texts. The data was analysed using a narrative approach. The findings are presented according to the research questions in narrative form illustrated by quotations. The findings of the study revealed that participants believed that classroom aggressive behaviour was caused by biological, social and economic factors. Biological factors included temperament, hormonal imbalances during the menstrual cycle, secondary changes during puberty such as physical strength and certain medical conditions. Social factors included jealousy between romantic suitors, group dynamics during sports competitions and school transitions, rogue prefects, gangs, peer pressure, sexual abuse, corporal punishment, family factors and religious and cultural beliefs. Aggressive behaviour was manifested in physical, relational, cyber and verbal forms. The study also revealed that aggressive behaviour resulted in negative effects that included students incurring physical injuries, committing suicide, experiencing depressive symptoms, anxiety, performing poorly academically and early school leaving. Recommendations for policy and further research were made. / Psychology of Education / D. Ed. (Psychology of Education)