The results from the two datasets indicate that working-class background is associated with lower school grades and that low grades are linked to the level of involvement in crime. In general, the results show that there is a significant but quite weak relationship between social class and crime. A person’s social background can be assumed to influence a person’s life-chances and future welfare in different ways. Social class background is commonly considered to be a factor to take into consideration in various analyses of criminality. This study focuses on the association between parental social class, school achievement, and criminality among young people. The study hypothesizes that there is a relationship between class background and school achievement, and between school achievement and crime. It also examines whether school achievement is a mediating variable between class background and crime. The study builds on analyses of both register and self-report data. Tables, references and appendixes 1 and 2