Yes, you can always add or remove parents from a class, group or community, as long as you are the teacher of the class, the class administrator or room parent.  To remove a parent from a classroom:

1. Navigate to the class
2. Click on the Members tab (located at the top menu in your desktop or in the bottom of your classroom on your phone.)
3. Select the user you want to remove
4. Click "Edit"
5. Select "Remove from class"