Can I use the same paper topic for two different classes?
The best way to cover this is to cite the earlier paper in the new one. A citation can be to an &quot;unpublished&quot; work as well as to a published one.
Submitting the old paper in the new course would be a violation unless done with explicit permission, but you aren't suggesting that. You are planning to extend the earlier work in a different direction which is a perfectly good thing to do in any research or scholarly writing.
Many scholars cover &quot;the same topic&quot; in separate papers so long as they have new things to say and also cite the earlier work.
If you want to be really clear, cite the old work and also include a copy of it with the new paper when you submit it. It can be hard to find &quot;unpublished work&quot; as well as citations of &quot;private communications&quot; and such other things that require citation. No one can make any claim of improper behavior as long as you are completely transparent, as you have been so far.