Troubleshooting Issues with the Apple TV

Real quick, there are a couple of options that you may find useful:
First, AirParrot gives you the ability to either Mirror (duplicating your display on both your computer and the projector) or Extend (have two different sets of windows open on your computer's display and the projector).  Just click on which option you want, and off you go (Display 1 is the option for mirroring)!
However, AirParrot also gives you the option to send only a particular window to the Apple TV.  That means that you can send a video playing in a Google Chrome tab to the projector, while working on a LibreOffice document on your desktop.  You can do this by selecting "Specific App," then selecting the program.  If you have more than one window in that program open (for instance, you have two Google Chrome windows open), then you can select which window you want to send after that.
Finally, AirParrot works by using the wireless network in the building to send video from your computer to the Apple TV.  As a result, projecting wirelessly can be stressful on the network, especially when there are lots of laptops on the network at the same time.  If you are noticing that the network is becoming very slow, or have even been disconnected from the Apple TV, you can try lowering the quality of the stream so that the network is more stable.  To do this, click on the AirParrot icon, and go to Preferences.  A box like the one above should appear.  Start by reducing the Video Quality first.  If you can't reduce that down any further, try lowering the Max Frame Rate.  Try not to touch any of the checkboxes.  This should help in case any network issues occur, but given the upgrades in the building there shouldn't be too many issues.