The emergence of gesture-based computing and inexpensive gesture recognition technology such as the Kinect have opened doors for a new generation of educational games. Gesture based-based interfaces make it possible to provide user interfaces that are more nature and closer to the tasks being carried out, and helping students that learn best through movement (compared to audio and vision). For younger students, motion interfaces can stimulate development of motor skills and let students be physically active during the school day. In this article, an evaluation is presented of a Kinect educational game where students learn to recycle using body gestures. The focus of the evaluation was to investigate potential advantages using gesture-interfaces in educational games, how the game affected the students' engagement, motivation and learning, and if there were any social preferences for playing the game. The results show that elementary school students get highly motivated and engaged playing a Kinect recycling game. The students also report that they learn from playing this game and prefer such game-based learning to traditional lectures. Finally, the students preferred playing this game as a multi-player game, where the boys preferred to play competitive while the girls preferred playing collaboratively.