Hi kgeorge,

Currently, the only way for you to get rid of the assigned assignments for a student is if he completes them. Also, the way the Khan Academy server works are that if your student completes the 5 assignments only once then it should mark the assignment in another class as complete. So if you can't get rid of the duplicated assignments then no worries because if he completes the assignments just once and masters them, then it will also show up as completed.

Hope this helps and if you have any other additional questions, feel free to ask.

Hi Kevin!

Just like the previous poster noted, if an assignment is posted in both classes and the student completed the assignment in the first class (before moving), it should show up as completed in the second class as well. 

Currently, there isn't a way to change an assignment for only certain students, but I will document your insights to share with our product team.

Thank you for being an active member of the community!

I'm not sure if this would help but under manage - active- assignment. Click on edit. unselect the students that you don't want to complete the assignments. I have used this method to take assignments from certain students.