Although the metaverse is a trending topic in several fields, it is not a new concept within the field of education. In this study, we followed the PRISMA framework and identified 37 articles since 2008 that researched the metaverse in education. We critically reviewed these articles, aiming to examine the evolution of the field's conceptual understanding of the metaverse in education, identify its applications and effects, as well as synthesize the technical solutions and adoption challenges for implementing metaverse systems in schools. We found that the early empirical implementation of metaverse concepts in education mainly emphasized the characteristics of 3D virtual environments and avatars using the Second Life and OpenSim platforms. These traditional applications were found to be effective in supporting various teaching methods and enhancing students' learning experiences and outcomes. In recent studies, more advanced technologies that pursue the fusion of physical and virtual environments (e.g. AI techniques, VR/AR devices, cloud platforms, wearable devices) have been incorporated into metaverse systems. However, the extent to which physical and virtual environments were fused in metaverse applications in education needs to be further clarified. We suggest that the conceptual clarity of the metaverse in education will keep evolving along with the technology development, and teacher preparedness for this new technical revolution needs more attention.