Students can only delete their announcements within a group. You can delete an announcement in the Announcements page or within an individual announcement.
Delete in Announcement Page
To delete an announcement from the index page, locate the announcement. Click the Options icon  and click the Delete link .
To delete multiple announcements at a time, click the checkbox next to the announcements you want to delete  and click the Delete icon .
Delete in Individual Announcement
You can also delete an announcement by opening the individual announcement. Click the name of the announcement.