From our experience, with students being un-enrolled via the SIS Import, if a student is unenrolled no one can access the attachment or submissions. However, if the student is re-added later, the attachments and submissions reappear, along with any grades.
For discussions, I don't believe they're removed, but you can manually remove them if they're no longer appropriate.
This has been our experience and what we have been told from support as well. However, this still comes up short for a task our faculty need to perform occasionally, which is to review student's work after they have dropped the course. At present the only workaround I'm aware of for this is for them to access the work on our test instance before the next sync from production.
Discussion posts definitely stay put. I just got done grading a discussion and noticed a few posts from students who had been dropped and weren't showing up any longer in Speedgrader.
I find it extremely annoying that all my records of a student completely disappear when a student drops a course—including all information about what groups they were in and how they were doing before they dropped.
It would be much more useful to have them flagged as dropped, without my losing all access to my records of them.
Reasons this matters:
Hey gasstationwithoutpumps. Have you checked out https://community.canvaslms.com/docs/DOC-12727-415241450?sr=search&searchId=abc4efce-6f10-4df9-860e-... It is now possible to "flag a student as dropped" in a manner, without deleting their enrollment. In other positive news, if a deleted enrollment is restored, the previous records are restored as well. Let us know if this works for you or if you have any questions.
I'm not the one deleting the students. When the Registrar sees that the student has dropped the course, my records of the student disappear from Canvas. This is usually the first notice I get that a student has dropped.
gasstationwithoutpumps, I completely understand. You will have to talk to someone at your school about modifying the way they process enrollments, but it is possible. When I was working for a college and we implemented this, it took a partnership of our eLearning, Registration, and Information Technology personnel to work it out, test it, and finally implement it permanently.
gasstationwithoutpumps, because of this very issue we added this report that our Financial Aid people have access to - https://community.canvaslms.com/groups/admins/blog/2015/04/14/assignment-submissions-report-programm.... This is a great report and has made everyone's lives a lot easier.