<p>Building students’ critical thinking has been a focus in Education around the world in recent years. The New Zealand Curriculum (2007) is no exception, with an emphasis on critical and creative thinking in its vision statement. However, no advice is offered on how to teach critical thinking. This study uses a qualitative case study approach to explore how teachers teach critical thinking through Philosophy for Children (P4C) and offers some guidance on this for teachers. One of the contributions of this thesis is the claim that the P4C approach enhances social justice by supporting diverse learners – children who need support to achieve at school – to develop critical thinking and language capability. The theoretical framework underpinning my research draws on Bernstein’s (2000) ‘democratic pedagogic rights’ to enhancement, inclusion, and participation, and Wheelahan’s (2007), Young’s (2009) and Young and Muller’s (2013) conceptions of powerful knowledge. While much attention has been given to the theory of powerful knowledge in tertiary and secondary education contexts, to date, very little research has explored what powerful knowledge might look like, in practice, at primary school. Therefore this study makes an original contribution by investigating this unexplored area. Participants in this research included 104 primary school students aged between 8 and 11 years old and their teachers (n = 4) from four diverse primary schools in New Zealand. The research data is drawn from four main sources: audio recordings of classroom discussions, semi-structured focus group interviews with sample students, open-ended interviews with teachers, and student thinking journals. Over a period of 6 months, classes held weekly hour-long P4C dialogues with a focus on both philosophical content and developing critical thinking language and skills. Students were encouraged to evaluate their philosophical and critical thinking both verbally and in written form. The methodological approach incorporates sociocultural perspectives highlighting the key role of language as a mediator and tool for thinking (Mercer, 2000; Vygotsky, 1962, 1978). Transcripts of classroom discussions were analysed both inductively and deductively, using Hennessy et al.’s (2016) coding system for analysing classroom dialogue across educational contexts and Daniel et al.’s (2005) matrix outlining the development of the dialogical critical thinking process. Observation of students’ everyday learning in the classroom, together with their and their teachers’ reflections, revealed that teachers played a significant role in shaping students’ language and critical thinking through modelling, facilitating dialogue, establishing a democratic classroom culture, making thinking visible, and innovating and personalising teaching according to their students’ particular needs. Both students and teachers developed a range of capabilities through participating in (or, in the case of the teachers, leading) P4C dialogue: resilience, receptivity, intersubjectivity. This thesis presents one of the first investigations into the practice of teaching powerful knowledge in primary schools and suggests that explicit teaching of disciplinary language enhances students’ critical thinking capability and constitutes powerful knowledge. A new conception of powerful knowledge is advanced, termed enhancing knowledge, which emphasises how disciplinary knowledge enhances and is complementary to other knowledges, such as social or cultural knowledge, without devaluing their importance. This term also seeks to avoid the potential dominant connotations of the word ‘powerful’. The findings of this study suggest that P4C can offer diverse learners access to enhancing knowledge which has the potential to improve equity in education and enhance social justice.</p>