Background. The study was prompted by observation that failure to obtain a positive postsecondary destination is significantly more prevalent in young people living in areas of greater social deprivation, and in males rather than females. Previous studies have shown that this could be linked to differences in social cognitive factors. However, these studies have been mainly correlational and no comprehensive assessment instrument was found to assess preparedness for the postsecondary transition. Aims. The present study examines senior high school student’s perceptions of the personal, behavioural and environmental factors that affect them as they prepare to leave school. It reveals the structure of these factors and how they vary with regard to social deprivation and gender. Sample. The participants were 1044 senior high school students (573 males and 471 females) who attended six urban high schools. Method. A pre-empirical, 50-item assessment instrument was constructed based on the literature review to identify the wide range of factors previously shown to be relevant to achievement of a positive postsecondary destination. This was then administered to participants. Results. Factor analysis indicated that young people’s perceptions about leaving school were best represented by thirteen factors. An ANOVA model indicated that young people living in areas of higher deprivation reported significantly lower levels of positive postsecondary destination self-efficacy belief, less experience of vicarious career success, less performance of career development tasks, greater perception of career barriers, greater endorsement of a fixed career mindset, and fewer career scaffolding attachments. Males, compared to females, reported less experience of past career success, and fewer career scaffolding attachments. However, despite being at greater risk of a negative postsecondary destination, males reported higher levels of positive postsecondary destination self-efficacy belief, greater experience of positive career-related emotional arousal, greater ability to set career goals, and greater levels of career optimism. Conclusion. Twelve significant main effects on the measured social cognitive factors have the potential to contribute to an explanation of why failure to obtain a positive postsecondary destination is more prevalent in young people living in areas of greater social deprivation, and in males rather than females. A new assessment instrument has been produced to inform an ongoing exploratory process to design, target and evaluate educational interventions to improve postsecondary destinations for all. Increasing internal consistency, external validity and generalisability of findings are all desirable. Some future interventions are proposed on the basis of the results, including greater use of positive career role models in career development programmes, career mindset retraining for high school students, and psycho-education on attachment-fostering behaviours for parents and professionals.