National testing and reform agendas, with their focus on school improvement, has led to increased collection and scrutiny of student data. The analysis of these data usually occurs at a school level, often by school leaders. What is less common is the opportunity for students to scrutinise their individual data and take ownership over the results and subsequent learning experiences. This paper reports on a study whereby students and teachers collaboratively interpreted mental computation test results and identify future teaching and learning directions. The findings showed positive outcomes for students led to changes in teacher growth and approaches to their teaching of mathematics.