The present investigation demonstrates the relevance of cooperative components in teacher-student interaction during the assessment of students' vocal performance from a social-behavioural perspective. It is proposed that, during the assessment of this performance, a social-behavioural interaction with cooperative components between teacher and student with the common goal of the occurrence of the theatrical phenomenon is recognized. It is also suggested that they both collaborate in the resolution of the conflict that arises from the acting performance, sharing the emotional development that this produces, and co-constructing that phenomenon. This exploratory study was based on the intersection of conceptualization from relevant literature and significant elements of practical classroom experience in vocal performance. It is concluded that a social-behavioural perspective of analysis allows to critically evaluate the cooperative interaction between teacher and student. This interaction could improve the teaching-learning process and the vocal expressiveness of students, by promoting a formative kind of assessment.