A cross-sectional survey of 6020 pupils aged 15 and 16 years in 41 schools in England found that 6.9% (398) reported deliberate self harm in the previous year, with 12.6% resulting in hospital presentation. Deliberate self harm was more common in females (11.2%) than males (3.2%). Factors associated with deliberate self harm in females included recent self harm by friends, self harm by family members, drug misuse, depression, anxiety, impulsivity, and low self esteem. In males, factors included suicidal behaviour in friends and family members, drug use, and low self esteem. The study highlights the need for school-based mental health initiatives to address this issue. Deliberate self harm is common in adolescents, especially females, and is often linked to mental health problems. The study suggests that school-based programs should focus on mental health education, screening for at-risk individuals, and helping teachers recognize such pupils. The findings support the development and evaluation of school-based mental health programs to address the issue of deliberate self harm in adolescents.A cross-sectional survey of 6020 pupils aged 15 and 16 years in 41 schools in England found that 6.9% (398) reported deliberate self harm in the previous year, with 12.6% resulting in hospital presentation. Deliberate self harm was more common in females (11.2%) than males (3.2%). Factors associated with deliberate self harm in females included recent self harm by friends, self harm by family members, drug misuse, depression, anxiety, impulsivity, and low self esteem. In males, factors included suicidal behaviour in friends and family members, drug use, and low self esteem. The study highlights the need for school-based mental health initiatives to address this issue. Deliberate self harm is common in adolescents, especially females, and is often linked to mental health problems. The study suggests that school-based programs should focus on mental health education, screening for at-risk individuals, and helping teachers recognize such pupils. The findings support the development and evaluation of school-based mental health programs to address the issue of deliberate self harm in adolescents.