Purpose: The aim of this study was to examine the associations between students' perceptions of the psychosocial school environment, health-compromising behaviours, and selected family factors. The analyses were based on data provided for the Health Behaviour in School-aged Children Study (2006). Design/methodology/approach: The data were obtained from 1,670 Finnish 9th graders. Logistic regression analysis was performed to identify the associations between school perceptions, health-compromising behaviours, and selected family factors. Findings: Educational aspiration was found to be the most influential factor connected to health-compromising behaviour among both genders, favouring students who were intending to apply to upper secondary school. The results also indicated that all the measured dimensions of school perceptions were associated with health-compromising behaviours: the more negative the perceptions, the more health-compromising were the behaviours. The associations were somewhat different between girls and boys. In terms of engaging in health-compromising behaviours, there was an association with school-related social relationships among boys. By contrast, among girls, other aspects of the psychosocial school environment were more important, for example engagement with the school and school strain. The role of parental bonding and monitoring was also significant among girls. Originality/value: The findings imply that attention should be paid to the health-promoting factors of the school, and to gender differences, not merely in planning prevention or intervention, but in everyday school life. (Contains 4 tables.)