Purpose: Since 2007, it has been mandatory for all vocational schools in Denmark to assess the prior qualifications of all students when they begin at the school and to use this assessment to divide students into different ability-based courses (streaming) with the aim of increasing the retention of students. The purpose of this paper is to explore students' experiences of being placed on a low-ability course by using case studies of two classes from separate vocational schools in Denmark with different practices regarding the streaming of students. Design/methodology/approach: The study draws on theories of student drop-out and engagement (Rumberger, 1993; Finn, 1989) and on the differentiation-polarization theory (Gamoran, 2010) concerning the effects of streaming students into ability-based classes. Two cases are described, representing on the one hand predominately positive experiences of streaming (better relations to teachers and peers) and on the other hand predominately negative experiences of streaming (low teacher expectations and negative peer-learning). Findings: The study shows that the two schools have organized streaming differently and that the students have very diverse experiences of being placed in a low-ability class depending on the way the schools organize streaming. Originality/value: The paper discusses the basic dilemma that schools face when they have to teach students with very diverse backgrounds and levels of engagement. The study shows that the division of students into separate streams involves a risk of reducing the level of engagement among students in the low-ability courses, but it also suggests how streaming can be organized to increase the engagement of students and possibly reduce their risk of dropping out of vocational education.