„Educating a class where students have a similar achievement level has been seen as more efficient and less demanding for the teacher than educating a class with students with very heterogeneous achievement levels.“
Paule Schaltz u. a., „The Effect of Ability-based Tracking in Secondary School on Subsequent School Achievement“ in „British Journal of Education, Society & Behavioural Science“ 4(4), 2014, S. 442