This paper investigates how a teacher in a rural school in Namibia teaches science. Of interest to us is the nature of the classroom discourse in constructing scientific knowledge that is meaningful to students. We draw on the work of Vygotsky (1978) in order to understand teaching/learning as dialectically entailed and to understand the notion of scientific and spontaneous concepts as distinct from science concepts, and operationalise his pedagogical theory utilising Hedegaard's (1998) notion of the double-move in pedagogy as fundamental to meaningful engagement. Through a detailed analysis of one teacher's pedagogical discourse we show how the linking of scientific and spontaneous concepts can either facilitate or hinder learning. Our analysis points to the importance of co-constructing meaning in the class, between teacher and taught and illustrates how analogies and metaphors can fail to create meaning in a classroom if the teacher does not recruit the learners' own everyday concepts.