Geospatial technologies, such as geographic information systems (GIS), remote sensing, and GPS have been used in a variety of educational settings to help improve student learning. A sample of 53 high school seniors was recruited from the Geospatial Semester (GSS), a course that emphasizes the use of GIS for problem-solving and students in AP Physics and AP History served as a comparison. GSS students' spatial thinking and problem solving improved across the school year in contrast to Comparison Group. Results suggest that GIS-based instruction can be used to enhance students' use of spatial reasoning when solving STEM-relevant problems.