This paper examines how writing produced within school-based practitioner research can function in framing and guiding both classroom practice and the research process itself. It outlines a model from Saussurian linguistics for analysing text, widely used by post-structuralist writers. In this model the meaning of the text depends on an evolving relationship between the words within it. An analogy is drawn with practitioner research, which is characterised as the generation and analysis of a sequence of pieces of writing, whose meaning can be derived through analysis of the relation between the successive pieces of writing produced. This model is employed as a framework for understanding, monitoring and influencing changes in practice. Examples are offered from a masters course for practising teachers.