If your Chromebook screen is enlarged or magnified that means that a student has changed one of the accessibility settings.  You can use the following steps to correct the issue:

  1. Move your mouse to the bottom right hand corner of the screen until you see the clock, wifi, and battery indicators (you may have to move the mouse "outside" of the screen due to the screen being magnified)
  2. Click the clock
  3. Click 'Accessibility'
  4. Click 'Screen magnifier' if it is checked
  5. Click on any empty space on the Chromebook's screen

If this doesn't correct the issue please submit a support ticket on this website.