Teacher recommendations are an important factor in the process of track placement, but research has shown that they are biased by pupils' social background. Pupils from higher socio-economic backgrounds are more likely to get the advice to enrol in an academic track than pupils from lower socio-economic backgrounds, irrespective of prior achievement. Previous studies looked primarily at individual pupil or parent characteristics and their influence on teacher recommendations. However, in this article, the authors argue that the class context forms the frame of reference within which a teacher forms his/her recommendation for pupils. Therefore, this article investigates class composition effects on teacher recommendations at the transition between primary and secondary education in Flanders. More specifically, we look at the socio-economic, ethnic and ability composition of a class. Multilevel logistic models were tested on data collected in 36 primary schools in the cities of Ghent and Antwerp in May 2015. The results show that only the ability composition of the classroom exerts a frame-of-reference effect on teacher recommendations for academically versus practically oriented tracks. A pupil with a low individual ability in a low-ability class was more likely to get the advice to enrol in an academically oriented track than an equally able pupil in a high-ability class. This study demonstrated the limited importance of class composition in teacher recommendations, but calls for more research on teacher bias in the process of track assignment.