Augmented reality is a similar technology to VR with one key difference. Rather than attempting to remove the user from the current setting, AR takes the user’s current view of the world and layers additional data on top of it. This augmentation allows the users to gain context, see detail and receive information they otherwise couldn’t.
Some AR systems don’t require HMD and can be run on smartphones. AR on a smart phone, though less immersive, is cheaper, easier to understand and something a group of people can experience together. On that basis AR is a great option for a classroom environment.