Your screen is no longer "optimized" for your laptop.  It has been optimized for the Viewsonic viewboard.

Please go to "System Settings" > "Displays" (screenshot 1).

Please select the dropdown next to "Optimize for", and change it from your Apple TV/Viewsonic to your laptop (screenshots 2 & 3).  Your laptop is named for your school site & your name.  Your Apple TV or Viewsonic will have your school site & room number in the name.

If you do this once, it should stick to this setting.