Multilingualism as a resource in the science classroom This study has two main aims. The first is to study and analyze authentic student conversations in a natural science teaching context in which second language learners are able to use both their first and second languages. The second is to examine whether switching between languages could be a resource for the students’ learning in the subject and, if so, in what ways. An underlying aim concerns how code-switching can help students to bridge the differences between everyday modes of language and more scientific modes. The analysis focused on 28 typical and representative code-switching situations between Swedish and Arabic, which arose in authentic science instruction situations. Transcription was performed together with an Arabic-speaking language teacher. The functions of the selected code-switching situations were analyzed based on a study of Appel and Muysken (2005). However, quantifying and categorizing code-switching situations based on their functions proved problematic. The analysis revealed the functional complexity of code-switching, whereby one code-switch often serves several different functions simultaneously; this is also consistent with previous research (Cromdal, 2000; Gumperz, 1982; Rampton, 2014). Instead, our analysis focused on the students’ linguistic movement between and within different discourses in the natural science learning. We used two main discourses: the students’ everyday practical experience of the world, and the natural science subject-specific discourse that students encounter in the school science instruction context. We also used discourses related to students’ social and cultural backgrounds. To describe students’ ability to move between discourses, we use the term discursive mobility (Nygård Larsson, 2011). The study was conducted with students at a multicultural school, where all of the students are multilingual, located on the outskirts of a large Swedish town. During data collection, the natural science subject was “photosynthesis, combustion, and ecological relationships.” In an attempt to create a language development instruction, the teacher used a genre pedagogical approach (Rose & Martin, 2012). The study followed 11 science education lessons using three video cameras and two voice recorders, and the collected material comprises to a total of 28.5 hours of student conferences and teaching sequences. Student texts and instructional materials were also collected. The analysis showed that most of the 28 different code-switching situations were used in order to increase the understanding of the natural science subject matters. The analysis also indicates that concretizing and relating the subject matters to everyday events helps the students understand abstract concepts, and is therefore a resource in the learning process. This is usually done by using both languages and often in code-switching between languages. In other words, the switching between first- and second language facilitates the use of the available languages, and helps increase students’ communicative spectrum which is supported in previous research (Creese & Blackledge, 2010; Wigerfelt & Morgan, 2011). Code-switching occurs within linguistic loops between discourses, which are an important condition to describe and develop new knowledge in the field. The students’ everyday experiences are often expressed using their first language, which means that the linguistic loops constitute a movement both between national languages and different discourses or use of language (modes of expression). On a more general level, it appears as though the students’ ability to use all their linguistic resources expands their discursive mobility (Nygård Larsson, 2011). Linking the natural science subject content with the students’ own experience enables code-switching, which, in turn, enables the students to contextualize subject matter as a precondition for deeper understanding. We can see important implications in relation to the results of the study. For example, the fact that some newly arrived students had started their schooling, and developed a basic knowledge of science, in their home country offered the opportunity to continue the development of knowledge in a language that makes this possible. We will therefor assert a flexible and multilingual education, where multilingualism and code-switching is perceived as a resource to support such development. Creating an expanded continuity between previous education, language development in both languages, and subject-specific teaching, leads to improved achievement for these students. Our study suggests that teaching situations that allow and encourage switching between languages and different modes of expressions can be an important tool in this development.