External suspension from school is a common disciplinary practice in traditionally English-speaking countries. Few studies have sought student perceptions of school suspension, as well as measures of problem behaviours and emotional problems, and known factors that influence the development of antisocial behaviour, to examine associations between these variables. Three hundred and four adolescents, aged 12-17 years, from five schools in southern Australia completed a self-report questionnaire that asked about behavioural and mental health problems, and risk and protective factors known to be associated with suspension. Seventy-four of the participants had been previously suspended from school at least once. Having been previously suspended was associated with a greater level of problem behaviours and emotions, poor family management, low school commitment, reduced supportive teacher relationships, and interactions with antisocial peers. School suspension appears likely to be applied to students who lack the ability to self-regulate their behaviours and emotional problems in the classroom. By excluding students from school, pre-existing behavioural problems may be exacerbated by diminishing school protective factors and increasing exposure to known risk factors. Adolescents most at risk of being suspended would benefit from alternative school behaviour management policies and procedures that maintain the school as a protective factor.