This thesis investigates how principals in neighbourhood secondary schools in Singapore manage their lowest stream, the Normal Technical (NT) students, in their schools. The study was guided by three research questions: (1) What are principals’ perceptions of streaming as a way of organising students in secondary schools?; (2) What perceptions and expectations are held by principals in neighbourhood secondary schools regarding NT students?; and (3) Do the principals' perceptions and expectations of NT students influence their school management with regards to streaming and the provision of opportunities for curricular and co-curricular programmes? The aim of the study and the research questions made the use of the interpretivist paradigm and qualitative research methods most appropriate. The study also adopted a symbolic interactionist perspective, realising that people make sense of their lives and experiences through interaction with others around them. The study exemplifies the methods proposed by grounded theorists (Glaser, 1992; Strauss & Corbin, 1990). Participants were principals of neighbourhood secondary schools. Data were collected using semi-structured interviews and documents over a period of approximately 36 months. Through the series of interviews a picture emerged of principals’ management approaches of their NT students. The grounded theory that emerged – the theory of ‘selective engagement’ – comprises a threefold typology of principals and three categories. The three categories are respectively: (1) Paradigms; (2) Conceptions; and (3) Management. The theory proposes that principals can be classified as ‘realists/pragmatists’, ‘innovators/improvisers’ and ‘nurturers’ according to the extent they selectively engage their students in the eight management areas: (1)Streaming/Lateral Movement; (2) Monitoring; (3) Deployment of Resources; (4) Subject Offerings; (5) Enrichment Programmes; (6) Managing Discipline; (7) Leadership Opportunities; and (8) Treatment of Students. The study shows how participants manage their NT students selectively in answer to the third research question. This gives rise to three discernible patterns of responses forming the basis of the threefold typology.