Computer games are very popular among children and adolescents. In this respect, they could be exploited by educational software designers to render educational software more attractive and motivating. However, it remains to be explored what the educational scope of educational software games is. In this paper, we explore several issues concerning the educational effectiveness, appeal and scope of educational software games through an evaluation study of an Intelligent Tutoring System (ITS) that operates as a virtual reality educational game. The results of the evaluation show that educational virtual reality games can be very motivating while retaining or even improving the educational effects on students. Moreover, one important finding of the study was that the educational effectiveness of the game was particularly high for students who used to have poor performance in the domain taught prior to their learning experience with the game. (Contains 3 figures and 2 tables.)