It is possible to delete a photo that you posted in a class page.

• Select the name of the class 
• Click Library on the bottom menu > Photos on the top menu > and the Picture you would like to remove 

• After clicking on the photo, click the Trash icon, and then Delete Permanently. 
• For Desktop: click Options, and then Delete Permanently. 

There is another way to remove a photo from a post:

• Click on the Arrow icon on the top right of the post
• Click Edit Post
• Click the X icon on the top right of the picture
• The picture should disappear from the post
• Click Post to save your changes