The work of teachers matters in many different ways. Not only do they provide students with the knowledge and skills needed to thrive in the labour market, but they also help develop the social-emotional skills that are vital for students’ personal development and for their active citizenship. But how do teachers best achieve this? By linking 2018 data from the Teaching and Learning International Survey (TALIS) with evidence from the Programme for International Student Assessment (PISA) – known as the TALIS-PISA link – this report aims to identify the teacher and school factors that matter most for student achievement and social-emotional development. The report uses a data-driven approach – based on machine learning and standard regression analyses – to identify the dimensions that are most strongly linked with student outcomes, and then combines this with a careful review of theory and previous research to analyse and interpret the findings. These findings provide a rich illustration of the many ways in which teachers and school leaders might influence the success of their students, acting as a tool for educators to reflect upon their own practice. Finally, the report offers several directions for education policy.