Denominational secondary schools in Scotland have been an influential means by which Catholics have achieved full social citizenship. Most of the Catholic population of Scotland has its origins in late-nineteenth-century migration from Ireland into low-skilled occupations. Although the church built a system of Catholic primary schools, it could not afford to extend this for secondary education, and so a compromise of 1918 allowed the state to take over the funding and management of almost all Catholic schools while the church retained a role in appointing teaching staff. The resulting public-sector secondary schools provided the Catholic population with unprecedented opportunities. The patterns of social and educational change affecting Catholic schools are studied here using a unique series of surveys of school leavers covering the whole of the second half of the twentieth century.