Hi @elainew!.
When a term, course, and/or section date has passed, the courses and/or sections are said to be concluded. This puts them in a read-only (archived) state. Read-only means that the course is not available for submitting assignments, posting discussions, uploading files, grading, or any other action-based task within a course.
Additionally, notifications and messages are no longer active in concluded courses.
Individual users can also modify their personal notification settings by following "How do I manage my Canvas notifications?" guide.
Here is a wonderful resource for admins for you to consider: End of Year Guide for Canvas LMS
Have a great school year!