Whole Institution Approaches (WIAs) to sustainability in education emphasize the strong link between the socio-physical environment and the learning processes and outcomes. However, there has been a lack of instruments for quantifying the implementation of WIAs based on the experience of learners and educators. In this article, we present the systematic development, pretesting, validation and first application of a novel WIA-Scale (learners: 13 items, educators: 15 items). As part of a large-scale assessment in Germany (school education, vocational education and higher education; n = 2,985), we apply the WIA-Scale and assess how WIAs are related to the effectiveness of sustainability learning. Based on extensive validation, the scale quality was evaluated as high. The application showed that young people who experience more sustainability in line with the WIA feel strongly more motivated and empowered by their educational institution to contribute to sustainability. Also, regression modeling revealed that WIA implementation is the strongest of various predictors of how sustainable learners act beyond the educational institution. Further, educators who experience more sustainability in line with the WIA feel considerably more motivated and report more sustainable behavior. They also view Education for Sustainable Development (ESD) as more relevant and participate more frequently in training on ESD. For future use, we provide the WIA-Scale in its original version, a 7/8-item variant and a one-item proxy. The scale may be used as a process indicator for high-quality sustainability education and as part of organizational development. Overall, the study shows that experienced WIAs are measurable and highly effective for quality sustainability learning.
