Experience with geographic information systems (GIS) can improve students’ spatial skills and provide a foundation for success in STEM (Jant et al., 2019). Researchers and educators co-designed a GIS unit in which high school students learned to use ArcGIS software by exploring geospatial patterns in their local communities. Across three teachers, 134 students participated in the unit and completed a geospatial problem-solving assessment. Students’ performance on the assessment significantly increased from pre- to post-test. Students whose teachers had more GIS experience and completed graded GIS assessments scored higher on geospatial assessments and used more spatial language than students whose teachers had less GIS experience and graded on participation. Students’ expectancy, value, and cost of computer science varied across teachers, and may be linked to students’ ability to devote time to map-building and their engagement with a GIS careers guide. We discuss the impacts of teacher training and lesson implementation on students’ geospatial thinking.