This study surveyed and analysed four secondary school students' writing about a square. Sfard's discursive approach to understanding mathematical discourse was used to analyse the responses collected from 214 Australian secondary school students. The results showed that geometric knowledge was developed experientially and not developmentally. This in turn helps refining the development of a geometric learning progression, with the accompaniment of a set of validated assessment tools and learning tasks that seeks to deepen teachers' understanding of geometric reasoning and support student learning.