Assignment activity, hide students names when grading.

How can I make sure that teachers cannot see the students names (identity) when they go in to mark/grade their assignment? Unfortunately I forgot to enable Annonymous submission. As you will find in this assignment activity (link attached) i selected under permission that teachers do not have permission to see students names and identity. However the result is not that... teachers see students names when grading. Please shed some light here . This is an urgent matter for me with their exam assignment needing to be marked. I have searched online and the forumn, but not yet found a reason.