Collaborating in a group and leading group work are often used in the modern language classroom. However, it still seems relevant to find an effective way to assess group discussions and to identify problems that students experience
when they have to mediate texts and concepts or collaborate on shared tasks. This paper analyzes the engagement of students with a task to mediate and discuss information in a group and how students approach the tasks at the B1 and B2 Council of Europe (CoE) or CEFR levels. The objective of this paper is to show that group discussions can be used for the formative and summative assessment of mediation skills as they are described in the CEFR Companion Volume (CEFR/CV; CoE 2018). We will describe the process of how learners can receive global achievement marks for mediation on par with analytical marks for interaction, discourse management, range, accuracy, and phonological control. We also provide an example of how assessment of a group discussion can be done by giving students a global achievement mark for mediation and analytical marks. The outcome of the research is a test that can be used in the classroom and to provide criteria for assessing mediation when it is part of a group discussion.