The research starts from the assumption that hierarchies of students' achievement in mathematics are social constructions. To describe these constructions as "social" bears two meanings: Micro-sociologically, teachers and students negotiate the criteria for participation and achievement by means of interaction (Mehan 1992); macro-sociologically, society is constituted by hierarchical relations of power and control and these relations are reflected in students' hierarchies of achievement (Bourdieu & Passeron 1970). The focus of the research is on those practices of organisation, interaction and regulation within the mathematics classroom by which the hierarchies of achievement are constructed.

Empirical research on constructions of disparaties of achievement has proved Bernstein's (1990, 2000) theory of pedagogic discourse as a solid theoretical ressource for linking the micro-sociological and the macro-sociological perspectives described above (e.g. Bourne 2003, Hoadley 2007, Morgan, Tsatsaroni & Lerman 2002). This link is generated by the concepts of "classification" and "framing" which are central for Bernstein's explanation of classroom interactional practice. While "classification" considers the relation between contexts (e.g., domains of practice, knowledge, agents, space ...), "framing" regulates the relationships between transmitters and acquirers within a context. Bernstein (1990, 2000) holds that different combinations of classification and framing values of classroom practices are stongly related to learning opportunities (access to knowledge) and outcomes.

The values of classification and framing are used in the research to analyse the relative importance of instructional and regulative discourse for the construction of hierarchies of achievement in mathematics classrooms. The concepts of "instructional discourse" and "regulative discourse" are also from taken from Bernstein (1990, 2000). The instructional discourse is a discourse on the subject matter while the regulative discourse conveys meanings of the moral order (incl. students' behaviour). Bernstein emphasises that this distinction is only analytical and that, in classroom reality, the instructional discourse is embedded in the regulative discourse.

Bernstein's theoretical framework has been characterised as highly abstract. Accordingly, it does not inform about how the embeddedness of the instructional in the regulative discourse might affect the constrution of hierarchies of achievement. However, my hypothesis is that this embeddedness is acted out differently for high-achieving and low-achieving students, and research should be able to make the differential embeddedness visible. The research question is: How do teachers value the students' constributions to the instructional discourse and the regulative discourse within different contexts? These contexts are made by, one, a group of high-achieving students (in a German Gymnasium class); two, a group of low-achieving students (designated to future manual labour jobs).

The focus is on students' learning of mathematics because in mathematics teacher evaluation of student contribution is a particular constitutive of interaction patterns (Bauersfeld 1988, Stodolsky 1988). Although the German school system with its emphasis on early and radical selection of students on a systems level might be considered an extreme case (and thus a promising context to investigate in), there are explicit selection and setting and streaming practices in most other (not only) European countries, making the results of the research relevant beyond the German context.

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