When I copied a course to this term's shell, I reset all dates for the course. I have over 100 discussion topics, most of which are used each term, stored in the Discussions area. In the new shell, there are a few old discussion topics that are currently not being used for the course. They have been removed from the Modules area, which is the only content area open to students. Students should only be able to enter discussions through Modules.
A student was able to enter a discussion that is no longer a part of the course, but is still sitting in the Discussions area. I am now forced to give a grade to a student for posting to a discussion invisible to the class.
Testing this, I found, through the Student View, that a student can click on To Do or Coming Up from the Home page and then go to the top of that page and click on Discussions. Even though I do not have a live link to Discussions, this would allow students to access the entire list of discussions. I am constantly sending messages to students reminding them to click on Modules to see all of the discussion threads each week, rather than click on To Do or Coming Up.
Why does Canvas allow students to access content that is not a part of the current course and is stored in a “hidden” area? How can I prevent students from gaining access to Discussions?
Canvas offers a great feature which should enable you to completely hide these from students. Discussions can be put into a draft state (unpublished) which will ensure no student can access them. The following Canvas guide should help you out How do I use Draft State in Discussions? You could unpublish the content in the course shell as well as any currently running courses, and students should no longer see this.
Something I have discovered in my travels is that the menu items in a course in and of themselves do not hide or unhide content from students, only access to the aggregated page of content themselves (such as the list of discussions). I have come across something very similar with this myself a few times with pages. We had content created en-masse within courses, then released on a schedule. However, as all the pages were published, students could see this content in the WYSIWYG editor (such as in discussions when they are writing a post).
This was something where we too, needed to focus on ensuring that content was in an 'unpublished' state until it was ready to be seen by students.
Hope this helps!