Purpose: An analysis of the relationship between discourse and cognition in the context of middle school science teaching is provided in this study. Teacher-led questions, cognitive demands and patterns of interaction were analysed for the discourse side of the study. The students' argumentation quality was explored for the cognition side of the study. Methods: Participants were an elementary science teacher and 19 seventh grade students. Socio-cultural discourse analysis was conducted in two phases: systematic observation (coding and counting) and episode analysis (contextual in-depth exploration). Findings: The student-led argument quality was found to be reduced due to close-ended triadic dialogues when the teacher overtly displayed follow-up evaluations and follow-up explanations. The argument quality was fostered considerably when the teacher staged timely and relevant follow-up questions, since more dialogic space on the side of the students had been created. The students' argumentations were observed at the highest levels when the teacher used low (e.g. understand) and high (e.g. analyse and evaluate) cognitively demanding questions together. These findings were also supported by the episode analysis, which aimed at representing the discursive-contextual compositions of the in-class implementations. The results showed that discourse (questions' cognitive demands and patterns of interaction) and cognition (students' argumentation quality) were found to be associated. Suggestions were made for science teachers and science teacher educators.