We assessed whether the level of time-pressure reported by a school's teachers is predictive of student bullying perpetration. We combined data from two surveys conducted in 129 schools in 2016: the Stockholm School Survey performed among students in grades 9 and 11 (n = 10,668), and the Stockholm Teacher Survey carried out among senior level (grades 7-9) and upper secondary school (grades 10-12) teachers (n = 2259). Multilevel path analyses showed that teachers' stress and time-pressure increased with declining school leadership functioning. Teachers' level of time-pressure was, in turn, positively associated with student traditional and cyberbullying behaviour, through its effect on the school staff's tendency (not) to intervene against bullying, but not through the teachers' stress level. We conclude that schools with leadership that provides opportunities for the teachers to focus on their main mission can counteract bullying among the students and therefore indirectly also to promote student health.