Only the administrator or a privileged employee can delete any comment posted. Students, parents, and employees (without privilege) can only delete comments posted by them.
At the top of your dashboard, click the module access icon > Collaboration > News to open the Latest announcements page.
In the Search news field, enter the title of the news to search, or click the View all to view all the news.
Select the news post.
Click on Delete.
For more information, watch this