Spatial thinking is an integral skill for geography students to develop. Whilst many spatial competencies have been identified by researchers, and the merits of GIS seemingly ubiquitous in the published literature, little work has been done into how students' spatial thinking skills can be assessed. Therefore, further investigation into the relationship between spatial thinking and performance and attainment is needed. This research investigates the impact using a geographic information system (GIS) has on students' spatial thinking skills and attempts to assess the extent using a framework. This was done through the design and implementation of two GIS-based interventions. This small-scale evaluation used qualitative methods to investigate students' and teachers' views. Student work was also analysed using the framework developed for the assessment of spatial thinking skills. The findings suggest that the use of a GIS does enhance, and in most cases improves students' spatial thinking skills, but, that spatial thinking is hard to quantify and difficult to measure progress in. Another benefit that using a GIS affords is the creation of engaging, contemporary and interactive lessons, using real data, from which students derive a lot of geographical value.