This thesis reports and discusses results from case studies of how two physics teachers process the language and subject content of textbook texts in interaction with their students, several of whom are second language learners. The overall aim is to study and contribute to knowledge about the didactic choices teachers make in relation to text-talks in linguistically diverse physics classrooms. In order to find out what might pose linguistic challenges for the students, the textbook texts used in the classrooms are also analyzed.

Data was collected through video and audio recordings in a year 5 and a year 8 physics classroom, during a period of nine and seven weeks respectively, where physics was taught by teachers who identified themselves as having a language focus in science instruction. In addition to the classroom observations, semi-structured interviews with the teachers were conducted.

The study is rooted in socio-cultural theory, including literacy and second language acquisition, and in social semiotics, including systemic functional linguistics (SFL) and multimodal perspectives. In the textbook texts, structural and lexicogrammatical features were analyzed. In the text-talks, the analysis focused on how language and content were processed in interaction with the students and what opportunities and limitations this offered the students.

The results reveal that the science textbook texts impose great linguistic demands upon the students. The results also reveal that both teachers carried out extensive textual processing in interaction with their students, which showed the teachers’ broad repertoire of didactic choices in connection with the text-talks. The text-talks offered an increased redundancy, opportunities to develop academic registers and to some extent to be socialized into disciplinary reading. Limitations were associated with the teachers not always being sufficiently clear about the purpose and implementation of the text-talks, the language focus sometimes taking the focus off the subject matter and the teachers' use of everyday language not always being an asset.