This is because Nickname is not set to display to Parents. To set profile publish access, navigate to:

  1. Core > Settings > Profile
  2. Click Profile Publish Access
  3. From the drop-down menu, select the role for which you would like to publish information (Student)
  4. Click the role-to-role link to publish that role's information to another role (Student to Parent)
  5. Click Edit
  6. Select the Radio button for "Reset Publish Fields for ALL Users"
  7. Mark Nickname and Middle name
  8. Click Save & Confirm
  9. Click Confirm
  10. Click OK