Virtual Reality (VR) has long been a promising medium for education, especially when an understanding of 3-dimensional relations is necessary for the learning outcome. Up until now, the use of VR has been reserved for research at universities and expensive custom training applications due to high equipment and maintenance cost. However, with the recent introduction of cheap, consumer-friendly head-mounted-displays (HMD) and motion tracking sensors the possibility of VR becoming a widespread educational tool is suddenly present. In this paper, we describe the evaluation of a VR application teaching astronomy to middle-school children using the consumer-grade VR equipment suitable for a classroom setting. The learning outcome and engagement is measured and recommendations for future applications are provided. We hope our research may provide a base of knowledge on how to make effective and engaging educational VR applications.