Geosites are suitable locations for field teaching of Earth sciences. However, their educational potential does not always correlate with the scientific significance of geosites, as for educational purposes, the visibility and comprehensibility of the phenomenon are much more important. The educational potential also depends on the target group, as a location suitable for the education of adults may not be suitable for the education of younger pupils. The article describes an experiment in which a method of assessing the educational potential of geosites was developed based on the analysis of the outputs of inquiry-based learning tasks during field teaching on geosites. The method is based on the gradual implementation and evaluation of the inquiry-based learning program for different categories of target groups, proceeding from more experienced and older to less experienced and younger participants. Although the method is relatively time-consuming, it provides very accurate results that can be applied to different target groups. The use of this method can help schools, institutions implementing extracurricular education programs, and geoparks to identify correctly suitable geosites.