The article presents the results of an educational development project conducted from 2017-2018. The aim of the project was to identify common subject-specific concepts of quality regarding stage performance, with a focus on ability to perform dramatic text. Student assignments in the form of stage performance were video recorded. Thereafter, the documentation was examined and discussed by a team of teachers. Audio recordings from the discussions were analysed using phenomenography. The results are presented in four qualitatively different categories of descriptions and in aspects of the different ways of knowing involved in the phenomenon. In this article, it is argued that this kind of research is essential for designing and developing teaching instructions, giving competent feed-back, and efficiently assessing and grading the students’ work. Moreover, it is argued that being able to identify such quality differences of stage performances is also essential for the student in the future work as an upper secondary school teacher.