Hi Mrs. Forbes,

It is not currently possible to have past unfinished work automatically come before current assignments in the queue. Students can still see their past work by viewing their past assignments tab. 

You can extend the due date for the past assignment(s) manually so that it shows up at the top of their assignments (you can do this by selecting the Manage tab on the class page and selecting Actions on the assignment you want to edit) -- however, this will not show the assignment as being turned in late.

I hope this helps! Please let me know if you have any further questions.

Somethings I change the due date for old assignments to future dates so that the students can see the assignments that they did not complete. They often forget to look in the past-due bucket.