How do I unjoin a group?
If your instructor or site administrator has allowed you to join a group, you may also be allowed to unjoin (remove yourself) from it, depending on the group settings.
Go to Site Settings.
Select Site Settings from the tool menu in your site.
Select Groups you are a member of.
To the right of the group's title, select Unjoin.
View Groups you can join.
Once you have removed yourself from the group, it will appear under Groups you can join along with other joinable groups.