After analysing the TSA data, the English teachers of Fung Kai No.1 Primary School prioritised writing as one of the major areas to be addressed. They would like to explore more effective ways of teaching writing but also believed that having firm grasp of how to use data is no less important than knowing which approaches to choose to teaching writing. It was this belief that drove them to conduct an action research study leading to changes in the writing curriculum through the progressive use of data.