This is not a dissertation but a published article based on a study that looks at teacher beliefs, social class and underachievement. Describes the methodologies, findings and is published by the British Journal of Sociology.
If you have been asked to learn more about sociology and inequality in Education, then I imagine that this journal would have many excellent articles that can help enhance your knowledge.
Mirad Dunne & Louise Gazeley (2008) Teachers, social class and underachievement, British Journal of Sociology of Education, 29:5, 451-463
To link to this article: http://dx.doi.org/10.1080/01425690802263627