Differences in achievement between disadvantaged pupils and their more advantaged peers are a focus for policy in all parts of the UK. A gap in educational outcomes between pupils from less-affluent backgrounds compared to their peers is evident by the time they start school and only widens as they move through the school years. In 2018, nearly 80 countries participated in the Programme for International Student Assessment (PISA). PISA assesses 15 year olds' proficiency in reading, maths and science and collects data on a wealth of background factors via questionnaires from pupils, teachers and school leaders. This provides a unique opportunity to explore the impact of disadvantage on pupils from an international perspective, as well as a comparison across England, Northern Ireland and Wales on the devolved matter of education. This report focuses on reading, mathematics and science performance in PISA to answer three questions: (1) How well are England, Wales and Northern Ireland doing at supporting the reading, maths and science performance of disadvantaged pupils compared with other countries, and has this changed over time? (2) How do resilient pupils' (high-achieving, disadvantaged pupils') attitudes differ from low-performing pupils' from similar backgrounds and similarly performing pupils' from more advantaged backgrounds? and (3) In what circumstances do disadvantaged pupils tend to overcome barriers to perform better, and are there lessons that can be applied more widely? [For the research brief, see ED612577.]