The Education Reform Act of 1988 introduced a policy of open enrolment into English secondary education that was designed to enhance the scope for parental choice of schools. In the resulting 'quasi market' for education, state school admissions authorities can no longer deny most expressed parental preferences, and the majority of state educational funding follows pupils to the secondary schools that they attend. Accompanying these policy reforms has been a longstanding concern that the new school attendance patterns resulting from the enhanced choice present within an open enrolment system would further polarize the social compositions of secondary schools in England. This thesis employs recently developed individual-level databases such as the Pupil Level Annual Schools' Census (PLASC), along with GIS mapping software, to investigate the role that choice of non-local schools played in the degree of social segregation in English secondary schools in 2002. A detailed analysis of the data reveals high rates of non-local school attendance across many areas of England in 2002 as large numbers of pupils from all backgrounds bypassed their local schools in favour of non-local alternatives. Although non-local school choice was exercised by both disadvantaged and more advantaged segments of the schooling population, pupils eligible for free school meals were less likely to attend higher performing non-local schools than their more advantaged counterparts. The disproportionate gains made from non-local school attendance by more advantaged secondary pupils within the marketplace helped to reinforce local school hierarchies already strongly associated with performance and social composition. As the individual level pupil data in PLASC illustrates, the exercise of non-local school choice in 2002 produced school compositions that were more segregated by socio-economic status than they otherwise would be under a system of local school catchments. Thus, rather than helping to diminish the social segregation of secondary pupils resulting from pronounced residential segregation levels, the availability of parental choice instead further stratified most English secondary schools by socio-economic status in 2002.