This study deals with the writing of senior students in the subject English from two ACT secondary colleges. Whilst the written work analysed is from students enrolled in courses accredited for tertiary entrance, the ACT'S high retention rate and students' tendency to avoid 'non-tertiary' courses, ensures that the scripts analysed are wide-ranging. Broadly, this study rests on the theoretical approach to language and learning that came out of Dartmouth: that which is associated with James Britton. Its focus is twofold. In Volume I it presents a heuristic, describing its development and discussing the thinking, and learning students appear to do - and the writing they do - as a result of using it. The heuristic is called 'streaming' by the students who use it and is based on Vygotsky's notion of 'Inner Speech'. A key phrase that expresses a powerful or rich idea about the subject being studied is used as a starting point for student thinking. Students explore the layers of cognitive and affective meaning encapsulated in the idea, and perhaps extend the idea, in writing. The writing is very rough, and an act of thought whereby the meaning of the phrase is accommodated, rather than a communication to others. Students are asked NOT to think prior to setting pen to paper, but to let their writing 'bring their thought out of the shadows' by giving words to it. This avoids superficial or cliched response because the process of 'thinking out loud in writing' allows an interplay of cognitive and affective meaning that seems to lead students in to abstract thinking, generally by way of poetic abstraction. The 'streaming' that students do becomes the basis for further discussion or writing in a variety of forms. Volume II is given over to an explication, and use, of Graham Little's development and refinement of an analytical model for investigating language use. Based on the variables of situation, function and form, it enables the empirical analysis of 237 examples of writing from students who had used the heuristic presented in Volume I. The analysis indicates that students who use the heuristic write differently from students who do not. Their writing shows a wide range of function and form and achieves unusually high levels of abstraction. The thinking and writing that students do when using the heuristic is usually realised poetically and used as a basis for further writing. The range within the student writing indicates a high degree of language competence whereby students are able to write in different forms. Little's analytical model is a simple and powerful means of quantifying elements of school language in order to make qualitative judgements that are sensitive to the complex and holistic nature of language development and use.