For almost 30 years, the school subject Swedish as a second language (Sva) has struggled with poor goal achievement, a high proportion of unqualified teachers and a political lack of interest in multilingualism. With large flows of refugees in recent years, there is a considerable number of students in Swedish primary school who are in need of a school subject with clear assessment routines for more effective second language teaching.In order to make visible how assessment routines are used for second language development and thus enable the purpose of this qualitative study, semi-structured interviews have been conducted with seven sva-teachers at six different primary schools in a medium-sized city in northern Sweden. A conventional content analysis has been done based on the transcribed material, through coding and thematization.Based on Vygotsky's sociocultural perspective and Hattie's theory of visible learning, this descriptive study investigates how and why the interviewed Swedish teachers apply continuous assessment of students' second language development.The result shows that even if the sva-teachers in this study use the same assessment tool to make students' progression in the second language visible, it is not certain that the effect of the assessment is the same because the same assessment tool is used for different purposes by different sva-teachers.