Philosophy for Children is a school-based intervention currently implemented in more than 60 countries. This thesis examines the evidence regarding the effectiveness of Philosophy for Children for developing pupils’ cognitive and non-cognitive skills. Three different approaches were used. A systematic literature review was conducted of the evidence published in the last 40 years. A new comparative evaluation study was conducted with Year 5 pupils in 17 primary schools in England. The intervention lasted for an academic year, and a pre-test and (...) a post-test were given at the beginning and end of the school year to evaluate students’ critical thinking and creativity. Secondary data analysis of the National Pupil Database from the Department of Education was used to examine the long-term effect of P4C implementation on attainment. The results of 34 schools which implemented P4C during Key Stage 2 were compared with 14,791 mainstream schools in England which did not, and the same analysis was repeated based only on these pupils in both groups known to be eligible for Free School Meals during the last six years. The review results suggested that P4C generally has a positive impact on reasoning skills. In most studies, P4C also has a positive impact on literacy and some non-cognitive skills. However, the new comparative evaluation study found no evidence that P4C has a positive impact on Year 5 students’ critical thinking or creativity. This comparative study has some limitations in terms of design and inevitable attrition. The more robust secondary data analysis showed that students eligible for Free School Meals develop their reading and writing more after long-term P4C implementation than in non-P4C schools, during Key Stage 2. By combining all of the evidence from the review, comparative evaluation study and secondary data analysis, this study suggests that the implementation of P4C in primary schools is still worthwhile, both in its own terms and for its added benefits in terms of cognitive and perhaps non-cognitive outcomes. The programme is likely to help improve students’ reasoning skills. P4C can improve the literacy of disadvantaged students in the classrooms, relative to their peers, and so contribute towards closing the attainment gap between advantaged and disadvantaged students. However, the new evaluation creates a caution about what can be expected from P4C and, if it used, the programme may need adjusting in order to provide opportunities for practicing a wider range of thinking skills. (shrink)