M.Sc., Faculty of Science, University of the Witwatersrand, 2011 / This study was concerned with the constitution of the ‘legitimate text’ - a key construct in Basil Bernstein’s (2000) theory of the pedagogic device. The question the study sought to understand was: what is constituted as the legitimate text across the mathematics education literature, the official curriculum document, in the official assessment texts, and in the textbook used in the classroom observed for the topic of number pattern. These sources were compared with what was constituted as the legitimate text in a sequence of five lessons based on number patterns in Grade 11 in an inner city school. This was a qualitative case study, the methodology of which was framed by Bernstein’s theory which explains the sociological nature of knowledge, the implicitness and explicitness of the communication for the acquisition of the legitimate text and hence opportunities to learn. One teacher was observed while teaching number pattern to a G11 class in an inner-city high school in Johannesburg in South Africa. A sequence of five lessons was videotaped and transcribed. The documents were analysed. One broad evaluative event with numerous sub-events called input objects were used to chunk the data into more manageable units of analysis. A framework emanating from the literature and from the analysis of the curriculum was used to present and categorise the legitimate text from the documents and the classroom. Kieran’s (2007) model of school algebra was used to do the analysis as well as Dowling’s (1998) model of domains of practice. The results of the study showed that the documents did not align with each other in terms of what they constituted as the legitimate text. It was found that the teacher aligned with the curriculum document. The results revealed that the teacher preferred working with numeric contexts. The consequence of this misalignment was that the documents created an additional work load for the teacher to understand and interpret them (documents).