When connecting to Airplay, you should be presented with a number of different devices to connect to. However, if the Apple TV allocated to your classroom is not showing, you will need to reset your machine.

1. Restart your computer.
    
2. Once rebooted, go to your System Preferences  either through the Menu Bar (shown below), or through Spotlight.
   
    
3. Select the Bluetooth panel.
   
    
4. Turn On Bluetooth, or turn it Off then On again if applicable.
   
    
5. Go Back to the main System Preferences  menu, then Click the Displays panel.
   
    
6. Select your Airplay Device (e.g. SCT JS 22.123).
   
    
7. You can then Connect to your projector via Airplay. For more information about connecting through Airplay, please visit THIS FAQ.