The current study analysed the relationships between socio-economic status, migration background, and non-cognitive factors and PISA reading and mathematics achievement. The results from multi-level analyses on Sweden’s PISA survey from 2018 indicate that both mathematics achievement and reading achievement are affected by SES, migration background, reading abilities, growth mindset, and the ability to master the content. Between-school level differences are explained by reading motivation and the mother’s educational level. Our findings stress the importance of both socio-demographic, socio-economic, and non-cognitive factors such as reading self-concept and growth mindset for both mathematics achievement and reading achievement.