Most large-scale summative assessments present results in terms of cumulative scores. Although such descriptions can provide insights into general trends over time, they do not provide detail of how students solved the tasks. Less restrictive access to raw data from these summative assessments has occurred in recent years, resulting in opportunities for data to be analysed at a deeper level. This article examines longitudinal data on students' performance on spatial numeracy tasks, with a specific focus on gender differences. Using an adapted Knowledge Discovery in Data (KDD) research design, data from a nationally-representative cohort were analysed over a five-year period. Results highlighted distinct differences in how males and females processed many of the spatial tasks. The opportunity to analyse summative assessment instruments at a deeper level offers more scope for worthwhile curriculum and classroom implications.