By default, students may only read announcements that have been posted by instructors and other instructor-type roles (e.g., Teaching Assistant). Permissions can be changed so that students may create, edit, delete, and even access draft versions of the announcements not yet published.
Select the Announcements tool from the Tool Menu of your site.
Select Permissions from the Actions Menu.
Modify the permissions for the roles listed.
Check the box next to each permission you would like to allow for a given role. (Deselecting a box will remove the corresponding permission.)
Note: You may see different roles listed depending on the roles that exist in your site. A role must be present in the site in order for you to modify its permissions. For instance, in a project site, you will see role for Access (i.e., students/participants) and Maintain (i.e., site owners/instructors).
Select Save to save changes.