A case study approach was used to examine the potential knowledge-transforming role of writing with 27, Year 12 chemistry students’. The study was prompted by changes to external chemistry examinations that required students to write connected discourse, and supported by the chemistry teacher's belief in the instructional value of writing-to-learn. The teacher modeled exemplars of laboratory reports, scaffold students in the use of a Laboratory Report Marking Rubric, and provided feedback about their reports. Data were obtained from examinations, an analysis of students’ laboratory books, interviews, an End of Intervention survey, observations and the teacher's in a reflective diary. Results indicated that the writing intervention impacted positively on students’ understanding of chemistry, ability to write laboratory reports, confidence, and examination scores.