This paper reports on findings from a three-year ethnographic study of twenty-four young people in northern England who were classified as not in education, employment or training (NEET), or at risk of becoming so. Drawing on conceptions of opportunity structure and educational marginality, the paper discusses the processes leading to young people becoming NEET after leaving school. It presents findings concerning the family backgrounds, school experiences and educational attainment of participants, and traces their initial post-16 destinations and their pathways to NEET status. Although most participants did not become NEET immediately after leaving school, restricted labour market opportunities and a lack of high-quality education and training for middle- and low-attaining young people exacerbated social and educational disadvantage. Over time, participants became increasingly restricted to marginal forms of learning. The paper argues that a focus on opportunity structures provides a powerful way of understanding these processes, and that alongside sustained NEET status, educational marginality should be of equal concern to policy makers.