Aim: To examine the associations between connectedness to family and friends, and school engagement, and selected health compromising and health promoting behaviours in a sample of New Zealand adolescents. Methods: A web-based survey was designed and administered to a random sample of 652 Year 11 students aged 16 years from all Dunedin (NZ) high schools between 30th July and 31st October 2001. Connectedness to family and friends, and school engagement were assessed, together with reports of various health compromising and health promoting behaviours. Logistic regression was used to determine the extent to which these family, friends and school variables were related to health compromising and health promoting behaviours. Results: School engagement was strongly related to both low levels of health compromising and high levels of health promoting behaviours. Connectedness to family was associated primarily with fewer reports of suicidal ideation and increased reports of physical activity. Connectedness to friends was associated in the main with increased reports of health compromising behaviours. Conclusion: This study reinforces the importance of school and family as support networks for young people. School may well play an especially important role in health promotion among young people. The mechanisms by which engagement with school operates need to be explored further.