In this text I focus on assessment as a key notion when it comes to investigating power relations in mathematics education. Taking the perspective of the mathematics classroom I investigate, through a foucauldian concept of governmentality, how students and teachers on a daily basis are institutionally governed through assessment discourses. Assessment is in this text understood as a broad notion incorporating feedback in classroom interactions as well as testing. The main purpose of the text is to present a methodology for investigating how different students may experience different assessment practices in mathematics education and, hence, how they are more or less invited into the discipline of school mathematics. This text is also, in terms of its methodology, a for-runner to a project on assessment practices in mathematics education in relation to students with various language and socio-economic background.