This thesis is a comparative case-study of how teachers in England and Portugal conceptualise and respond to pupil diversity in the context of individual planning. The purpose is to compare the processes and underlying assumptions in the two countries, in order to understand the impact of cultural aspects and of system characteristics on the phenomenon of individual planning. The research was conducted through a nested case-study approach in 10 schools in England and six schools in Portugal. The methods used were interviews with practitioners and analysis of individual planning documents. This study was done by following the cases of 41 pupils, who were identified by their teachers as 'needing individual planning', over a two-year period. The most common form of individual planning mentioned in educational policy are Individual Education Plans (IEPs) for pupils with 'Special Education Needs' (e.g. UK SEN 2001 Code of Practice, Portuguese Law 3/2008). Despite the apparent similarities, what is meant by IEPs in educational policy varies significantly. In this study, a comparative analytical cultural-historical framework (Artiles & Dyson 2005) and a 'societal approach' (Hantrais & Mangen 2007) were useful theoretical resources to overcome these challenges. This thesis presents an original approach to individual planning by looking beyond 'special needs' and national boundaries. The research identifies responses associated with individual planning and problematizes this practice as a solution to the challenges posed by student diversity to schools. This process is done with reference to the unstated assumptions about normality and difference proposed by Minow (1990).The study concludes that teachers conceptualise and respond to pupil diversity through a formulaic problem-solving approach. This approach is based on limited repertoires that are underpinned by contextual factors such as educational policy. These repertoires are wider and more flexible in England than in Portugal.