Philosophiae Doctor - PhD / Framed by the South African imperative of widening epistemological access to undergraduate science studies, this research takes the form of a case study to investigate the educational affordances of an extended introductory physics course. Using theoretical tools from Legitimation Code Theory (LCT) (Maton, 2014a) – in particular, semantic gravity and semantic density – the study characterizes the pedagogical practices and student learning in this Extended course, in relation to a Mainstream course in the same Physics Department. Data was collected through classroom observations, observations of student groups working on Mechanics physics tasks, and interviews with students. Two external languages of description were developed in order to translate between the LCT concepts of semantic gravity and semantic density and the empirical data from the physics context. The first language of description was used to characterize the semantic shifts in pedagogical practices, using a Concrete-Linking-Abstract continuum. The second language of description drew on physics education research on representations (Knight, 2007; Van Heuvelen, 1991a) tasks. Semantic profiles (Maton, 2013) were then constructed to show the semantic shifts in the pedagogical practices and in lecturers’ and students’ approaches to physics tasks. The study has shown that the extra curriculum time enabled different pedagogical practices. The Extended course showed a steady progression in pacing, initially with a less compressed semantic profile, while the Mainstream course showed a consistent compression. The Extended course showed a greater prevalence of the Linking level, with more time spent at the Concrete level and greater semantic flow. The courses also exhibited different communicative approaches, with students in the Extended course more engaged in making the semantic shifts together with the lecturer. The Extended course used more real-life illustrations as a starting point, whereas the Mainstream course tended to use verbal problem statements. Looking particularly at how problem tasks were dealt with, the study suggested that the lecturers’ pedagogical practices in dealing with physics tasks influenced the way in which the students tackled these tasks. The semantic profiles showed a more rapid shift up the semantic continuum in the Mainstream pedagogy and student work, while in the Extended pedagogy and student work, the semantic profiles indicated that more time was spent initially unpacking the concrete problem situation and explicitly shifting up and down the semantic continuum. In terms of methodological contribution, this study has demonstrated the usefulness of LCT tools for characterizing pedagogical practices and student learning in a physics context. Furthermore, the study has linked LCT to physics education literature and to research on epistemological access and academic literacies in a novel way. It has modified Maton’s form of semantic profiling, through introducing the following: a more detailed time scale, gradations of semantic strength on the semantic continuum, and coding for interactive engagement in pedagogical practices. The study thus has important implications for how curriculum and pedagogical practices might better support epistemological access to disciplinary knowledge in the field of physics, not only at the Extended course level but for introductory physics courses more generally.

Philosophiae Doctor - PhD / It has been noted by Lin (2013) that studies on multilingual talk, as illustrated by code switching in the classroom, have been repetitive and descriptive, and have for a while not been underpinned by substantially new or different questions (Lin, 2013:15). First, many of the studies in the literature have, for instance, concluded that there is a functional allocation of languages (FAL) in multilingual classroom teacher talk (e.g. Baker, 2012; Martin, 1996; Probyn, 2006, 2014; Jegede, 2012; Modupeola, 2013; Salami, 2008), such that language „a‟ is used for presentational knowledge, and language „b‟ is used for explanatory knowledge, and these claims have not been subjected to sustained scrutiny. Secondly, codeswitching and translanguaging increasingly have been the dominant and exclusive frameworks used, and this has limited the kinds of insights that can be obtained or the kinds of questions that can be posed. Thirdly, where the effects of multilingual teacher talk on students‟ understanding or knowledge are at all captured in studies, such effects have either been based on researcher intuition or have not been the object of sustained empirical demonstration. Fourthly, many studies have assumed merely that it is the configuration of languages that produces claimed effects of multilingual teacher talk, and attention has hardly been paid to repetition of content or to knowledge structure. Fifthly, it is not often the case that studies or findings are presented in a nuanced form that takes into account the possible effect of different subject types, school types or levels of study. Sixthly, and overall, many studies making claims on the effect of teacher‟s code-switching or trans-languaging on students‟ knowledge do not theoretically engage with knowledge, beyond the distinction between presentational and explanatory forms of knowledge, thus illustrating what Maton (2013) regards as “knowledge-blindness” (that is, the paradox of limited engagement with knowledge structures in pedagogical research making knowledge claims). As a result, little is known about how specific units of knowledge are encoded according to categories in a theory of knowledge, how knowledge encodings interface with languages, and how composite knowledge structures-language profiles can be visualised. This study draws on Legitimation Code Theory Semantic and Terminology Theory in order to investigate the interface of language and knowledge in multilingual teacher-talk in science and business studies classrooms in Yola, North-Eastern Nigeria. This focus should make it possible to answer questions such as the following which, though important, have not often been posed on account of the limited engagement in the research on classroom multilingualism with theories of knowledge: a) to what extent is it appropriate to claim that there is a functional allocation of language in multilingual teacher-talk (in which language „a‟ is used for so-called presentational knowledge, and language „b‟ for explanatory knowledge)?; b) what kinds of encodings of knowledge occur in a set of science and business studies lessons?; c) given documented visual patterns of knowledge dynamics emerging from recent research in the sociology of knowledge (e.g. semantic waves, semantic flatlines both high and low, downward shift and upward shift), (Maton: 2013, 2014a, 2014b), what knowledge profiles are observable and how does language use in multilingual teacher-talk map onto these patterns?; d) how are any observed differences in the composite knowledge-language profiles to be explained?; and e) what effects do various language-knowledge profiles have on students‟ understanding of the lesson and on their demonstration of their knowledge? Data for the study was derived from transcripts of audio-recorded multilingual teacher-talk in two subjects (integrated science and business studies) as taught in grades seven and nine in four secondary schools (two private and two public schools) in Yola, North-East Nigeria. Findings show, among others, that it is not always the case that the official classroom language (English) is used for introductory discourses, and the non-official classroom languages are used for explanatory discourses. Findings further reveal that it is not primarily the functional allocation of languages that explains perceptions or empirical claims of enhanced student understanding. We also observed that the number of content iterations, combined with knowledge structures, is an important factor that enhances or explains the performance of students. While this research has paid a lot of attention to teacher talk in the classrooms in two sites in Yola, North-East, Nigeria, where the use of Hausa and Fulfulde languages by the students is mainly in the spoken form, it would be interesting for future research to replicate this type of study in an environment where the non-official language of the classroom is perhaps used more frequently in reading and writing.