To facilitate the professional learning of teachers and bring about changes in pedagogical practices, it is necessary to understand the process by which teachers grow professionally. Professional growth can be achieved when teachers work together to engage in professional experimentation and see results in terms of salient outcomes for their students. This paper reports on a study of teachers' pedagogical practices as they introduced adaptations to focus on personalising students' learning in mathematics. Two cases are presented to demonstrate how teachers in two schools used student mathematics test data to determine students' strengths and needs, in order to personalise learning experiences. The findings highlight how shared responsibility and purposeful use of student data can lead to positive professional growth for teachers and improved learning outcomes for students.