In this article, we assume that discursive language aspects of science education are highly intertwined with students' knowledge-building and meaning-making in science. In an empirical case study, we investigate secondary students' (ages 15 to 16) discursive language use during group interactions. The focus is on how students define and explain the content within everyday or scientific discourses and how their negotiations may influence discussion outcomes. The results suggest that students who can move between everyday and scientific languages benefit from this exchange, while students who only use colloquial language or relate the content to everyday experiences become disadvantaged. Furthermore, important general success factors are students' abilities to establish solid relationships between words, expressions, and scientific terms to discuss, explain, and evaluate the scientific content. The results show important differences in discursive use of language within various school environments.