Mathematical modelling is emphasised in curricula worldwide. Since 2006, mathematical modelling has been considered a fundamental process in the mathematics subject in Norwegian upper secondary schools. This study aimed to identify tensions in the approaches to mathematical modelling expressed in teacher interviews (N = 4) and framework discourses (KOM and PISA) by four characteristics of communication (word use, routines, visual mediators and endorsed narratives). The tensions identified encompassed students' abilities to make choices and decisions during modelling activities and connection to specific mathematical content or real-life situations. Teachers also questioned the relevance of mathematical modelling, even though the main reason for the implementation of mathematical modelling in education is to make school mathematics relevant for everyday life.