On the Groups page, click the gear icon next to a saved group. The "Share" button is visible with the number of users who are currently receiving notifications for changes to the group. The types of notifications these "subscribers" get are initially determined by which boxes you tick: web and/or email.
You can choose individual users and/or user groups. Everyone will get a web notification informing them that a group has been shared with them. After the group is shared with them, and they are subscribed to the notifications you determine, users are able to make their own changes to how they're notified of updates in group membership, including opting out of notifications entirely.
Adding or removing subscribers is similar to how it's done for analysis reports. To add users or groups, choose names from the dropdown and click "Share".
To remove users, X out their names in the "Currently Shared To" section, or use the "Remove All" link to remove all subscribers. After removing people, you can simply click "Cancel", or click out of the window; no saving or confirmation is needed. Note that these actions will remove notifications for users even if those other people have chosen to subscribe to the group on their own.
If you deactivate a student group, this automatically removes all subscriptions, including your own.