Social categories such as gender, migration background or socio-economic status, but also family situations or skills play an important role in the planning, carrying out and thinking about teaching. The ways teachers deal with these categories of diversity are manifold, - and they are also limited, as they are influenced for example by individual liking, curricular standards or specific educational promotion programs. Often teachers 'use' categories to reduce the principle uncertainty of social interactions as school lessons are while the 'use' is not always explicit but more often implicit and in this perspective not-'known'. According to the leading hypothesis of this paper the construction of diversity along social categories establishes specific orders of lessons that may for example become apparent in the assessments of the pupils by their teachers. This thesis states that implicit and explicit knowledge are neither the same, nor are they totally different, but linked in a specific way which constitutes and constructs pedagogical activities at the same time. To outline this thesis the relationship between implicit and explicit 'knowledge' is analysed in the contribution by interpreting empirical data from an ethnographical school research project using the example of construction of diversity in casual verbal assessments. However, in most projects of ethnographical school and lesson research it is not easy to identify constructions of diversity in 'pedagogical practices' (e.g. assessment), because the teachers usually refer to tacit praxeological dimensions of teaching in their doing lessons. Therefore in special we have to pay a close look to the logic of practices as a 'nexus of doings and sayings' (Schatzki, 1996, 89). In this praxeological understanding non-verbal and verbal practices are to be understood as social activities which refer to and construct social orders at the same time. Practices are regarded as the 'smallest social entity'. Besides this, the praxeological perspective on pedagogical practices also stresses the importance of practices not only for the development of every-day-life routines but also for the construction of durable and institutionalized structures (Reckwitz, 2003).