A vocal minority from dominating the activity. Equitable distribution communicates to students that the teacher expects them to be actively involved and able to answer. When this becomes a pattern, both achievement and motivation improve (Kerman, 1979).
To make the process work, however, the classroom must be managed to prevent student call-outs, which are answers given by students before the students have been recognized by the teacher. Call-outs usually come from the higher achieving or more aggressive students in the class, and if this becomes a pattern, the less aggressive and lower achieving students are often left out, equitable distribution is reduced, and general achievement is lowered.