The curriculum for primary school in Sweden articulates the contextual dependence of concepts used in science. The students’ ability in different situations to use the knowledge achieved makes it important to understand differences in the meaning of words in different contexts in order to avoid conflicts between the intentions of the writer and the interpretation of the reader. The theory of conceptual profiles takes into account the variation in classrooms, which is common in Sweden, and promotes the teacher to achieve better communication. In the workshop the diversity of participants’ backgrounds made it possible to study the importance of mother tongue for conceptual understanding. Thus, the workshop was focused on two questions: 1) What influence does the mother tongue have on understanding and communicating science concepts? 2) Will these influences (if present) affect student communication and assessment? Learning by doing filled the major part of the workshop with opportunities for discussion, sharing ideas, and suggestions for further development. Participants were given assignments to assess students’ answers in biology, physics, and chemistry. Assessments were based on performance criteria of students’ use of concepts to describe processes in different contexts. Our results indicate that mother tongue is important for conceptual understanding while academic traditions seem to be important in assessment.