This thesis studies the adherence of a talk-intensive approach to teaching and ‎learning in the Brazilian context. While classroom talk is often classified as monologic ‎due to being narrow and controlled by teachers, educational research has identified a ‎kind of collaborative and cognitively productive talk that positively affects learning ‎outcomes. This dialogic talk is rare in most classrooms. Many teacher professional ‎development programmes have been designed to bridge this gap. This project builds ‎on this vast literature to explore three key aspects in the development of a more ‎dialogic classroom talk: small-group work, conceptual learning, and whole-class ‎teaching.‎ To produce such a dialogic case, an intensive, small-scale, researcher-led ‎intervention was implemented in one primary school. The programme lasted for three ‎months and consisted of three modules, each focusing in one of the aspects ‎highlighted above. Data consisted of pre-post knowledge tests, audio recording of ‎small-group work, video recording of whole-class teaching, and interviews. Classroom ‎talk was analysed through both quantitative and qualitative methods. Within the ‎Brazilian research field, this study is arguably the first with such aims and scope.‎ In small-group talk, students spent only half of the time talking about the task’s ‎content, when they used one third of dialogic utterances. Group talk features varied ‎reasonably across tasks and no positive variation was found regarding dialogicity. It is ‎argued that the students did not appropriate the use of ground rules for talk ‎effectively. Although statistically significant, only small effects were found on students’ ‎learning (knowledge tests). This result was discussed in relation to the role of different ‎teaching modalities, talk formats, and classroom climate in promoting the co-‎construction of knowledge. The investigation showed how talk served as a means for ‎learning. More specifically, five types of explanatory sequences were identified when ‎teachers and students collectively built scientific explanations. In whole-class ‎teaching, episodes of teachers’ dialogic practices were analysed and revealed which ‎conditions favoured such emergence.‎ Overall, this research sheds light on the potentialities and challenges of dialogic ‎practices in a Brazilian primary school. The study contributes with new empirical data ‎by systematically mapping groups’ and teachers’ discursive practices over seven ‎tasks and nine lessons. Pre-designed classroom materials were very productive in ‎fostering dialogic talk and teachers made many different decisions to render their own ‎lessons more dialogic. Finally, the broad scope of this thesis—connecting ‎professional development, use of classroom materials, student learning, and ‎classroom talk— allowed putting forward recommendations for future intervention ‎such as duration, pace, content, data-based reflective inquiry, and dialogic culture.‎