You can restrict a discussion topic to a group that you've set up in your course site. Then only the students enrolled in the group will be able to see and participate in the discussion topic.
To add group restrictions to discussion topics that you've already set up, follow these steps. Note that you must set up groups before create group discussion topics.
- Go to the Discussions area in your course site.
- Create a new discussion topic.
Once you've completely finished setting up your discussion, you will want to know more about adding threads and posting replies to them. View the Participating in Discussions guide for more information.