This thesis explores primary school teachers’ technology pedagogical content knowledge and how this impacts on teaching practices in technology education, particularly formative interactions. Based in the interpretist paradigm and using case study methods, the two-year journeys of eight co-educational teachers from two primary schools and their technology education perceptions and practices are described. The first year (1998) explores existing teacher knowledge and practices and student learning. The second year (1999) traces the impact of a professional development programme aimed at enhancing teachers’ technology pedagogical content knowledge in relationship to formative assessment. The significant impact of a planning framework containing the categories of technological practice, conceptual aspects, procedural aspects, societal aspects and technical aspects is examined. Findings from the first year reveal that existing school subcultures, school policies and teacher subject expertise influence teacher classroom practices in technology. Planning, teaching and assessment were often related to social and managerial aspects rather than procedural and conceptual technological aspects. Hence, learning and formative assessment interactions focussed on these aspects rather than student understandings in technology. The second year explores the development of teachers’ technological knowledge through a collaborative, ongoing teacher development programme. The development and use of a planning framework exerted considerable influence on teachers’ constructing appropriate knowledge and understandings and on developing a technological knowledge base robust and distinct from previous knowledge bases. A complex mix of specialist knowledge is required for teachers to become competent, confident teachers of technology. It is important to decide on appropriate student learning outcomes and to transform teacher technological understandings to those suitable for students. Further, the study shows that improvement in classroom formative interactions, especially the provision of descriptive feedback, makes a strong contribution to enhancing learning. It confirms that enhancing teacher pedagogical content knowledge impacts on their ability to provide descriptive feedback. Embedding formative assessment in technology and undertaking it in a sociocultural, transactional, conversational and future-oriented way strengthens student technological learning. Student gains are made in technology when teachers focus descriptive feedback on specific technological goals, particular technological qualities of student work and the provision of advice on how to improve technologically. This study provides empirical evidence that teacher perceptions and practices in technology and technology education impact on the technological learning of students. The assumption that students’ learning of technology can be enhanced through enhancing teachers’ pedagogical content knowledge and formative assessment practices is justified.