To remove the filter you will need to edit the Settings for the Calendar.

To do this:
  1. Navigate to School Website > Websites > Select the appropriate website > Pages & Menus
  2. Select the Wrench icon for the Calendar Page
  3. Select Settings
  4. Unmark the category you no longer wish to display on the Calendar
  5. Select Save & Close.
This will remove the filter(s) for this Category from the Calendar.