This paper focuses on school choice and diversity in the UK (England, Wales, Scotland and Northern Ireland) in historical context. Drawing on primary and secondary documentary sources it assesses continuity, change and divergence, before addressing existing diversity and school choice, and academic outcomes. The 1944 Education Act and associated legislation established, in each country, a system of state-funded church and state schools, comprising, academically selective (grammar) and non-selective secondary schools, with test scores determining whether the child was allocated to a selective or non-selective school. The paper argues that there has been broad continuity in Northern Ireland, whilst from 1965 England, Wales and Scotland diverged when school systems were reorganized -- to a greater or lesser extent -- along comprehensive lines. From the 1980s, parental "choice" (and diversity) policies were implemented in all countries, albeit differently. It is argued that existing school diversity across the UK is associated with distinctive histories and political ideas, and with varying levels and types of school selectivity and social segregation. Furthermore, the institutional rules regarding who is prioritized for a school place in the event of oversubscription -- particularly in the case of selective and religious schools -- can constrain parental choice as they enable schools to "select in" and "select out" certain students. Whilst improving educational standards was a key goal for the Conservative government when it introduced market-oriented reforms in England, evidence points to improved academic outcomes being related to changes in assessment policy.