The introduction of the National Qualifications Framework and the associated assessment against Physics Unit Standards represents a major paradigm shift in senior secondary school assessment. The trend away from norm-referenced external national exams towards internal standards-based assessment has significant implications for curriculum delivery, student learning and assessment and moderation practices. The New Zealand Qualifications Authority claims that the National Qualifications Framework is a technically sound and publicly acceptable alternative to the established system. Moderation is a key plank of the Framework which aims to establish and maintain national consistency of assessment across different providers, improve assessment practices, assist in the development of assessor expertise and establish public confidence in the new qualifications. Critics have expressed doubts that the perceived national consistency and public confidence in national examinations may be lacking in internal assessment against Unit Standards. The Post Primary Teachers' Association has expressed concern that the workload associated with the assessment, reassessment and administration of Unit Standards will adversely affect the quality of curriculum delivery and student learning. The present research is an attempt to evaluate these claims and counterclaims. In this thesis the assessment and moderation of the Physics Unit Standards is used as a context to answer the question: Is assessment against the Physics Unit Standards a valid, reliable and manageable way of assessing the achievement objectives of Physics in the New Zealand curriculum? A range of qualitative and quantitative techniques was employed to monitor the quality assurance of assessment and moderation of the physics Unit Standards over a three-year period and describe its impact on teachers and students. The research established that assessment against the Physics Unit Standards was generally valid but that doubts remain about its suitability to assess conceptual learning, the micro-definition of learning outcomes and the lack of recognition of different levels of achievement. The moderation action plan was found to be effective in establishing and maintaining satisfactory comparability between schools. After the initial implementation period the workload was manageable for teachers but concerns remained about dual assessment and excessive administrative requirements. Teachers felt that the resources provided by the NZQA were generally adequate. The research identified a number of areas for improving the quality of assessment against the Level 2 Physics Unit Standards. Chief recommendations related to the incorporation of higher level skills, a broadening of the performance criteria, the recognition of levels of achievement including excellence, the elimination of dual assessment and a reduction in the amount of assessment.