Teachers can use a Screen View feature to see the current screens of classroom devices, and can even open apps on all the devices on the same time. (iphonehacks.com)
Other classroom devices can then wirelessly connect to that computer. (airsquirrels.com)
Tablets like Google's Chromebook are an ideal classroom device because they're relatively cheap, interchangeable, easy to manage, and provide access to a range of Google's educational software. (businessinsider.com)