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

  1. Click the clock
  2. Click 'Accessibility'
  3. Click 'Large mouse cursor' if it is checked
  4. 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.