Hi Michael,
The following may be able to help you
https://khanacademy.zendesk.com/hc/en-us/articles/229426567-How-can-I-edit-my-students-display-names-in-my-coach-reports-

When you add a name to each students​ username you could do the following naming each student followed by a number.
For example beside username name your students the following
Student 1.
Student 2.
Student 3.
Student 4.

Also we have a Khan Academy Ambassador so they will probably outreach and have a better idea and tips to your question.

I hope that this article could be one way to help in keeping your students identity private on reports.

Should you have any other questions I will be happy to help you.