Preliminary research on virtual reality (VR) suggests that this technology could be a powerful tool for education based on its immersive and dynamic attributes. The Virtual Reality Roving Vehicles (VRRV) Project at the University of Washington is exploring these possibilities by taking VR equipment into elementary and secondary schools for students and teachers to experience and use in building virtual worlds. The question of how to assess VR is particularly significant because of the theoretical conflict between traditional and constructivist learning approaches. This report presents an example of how the VRRV Project is using VR in schools and identifies significant factors for assessment. Junior high school students (n=120) integrated the building of virtual worlds into a curriculum on wetland ecology. With regard to this project and other VR uses, the issue of test reliability versus validity is addressed in terms of general education and using VR. The underlying psychological theories of information processing and constructivism are discussed in terms of developing a comprehensive paradigm to guide the application and research of VR. This discussion is followed by an overview of specific approaches for measuring learning in VR, along with hints and cautions about conducting educational assessment. (Contains 2 figures and 70 references.) (Author/SLD)