If you want to share a group of files with your students, place all of the files in a shared Google Drive folder. Insert that Drive Folder onto your Google Site page. Now every time you drop something into that shared folder it automatically appears (upon browser refreshing, of course) on the page with the inserted folder.
There is no need for placing the file in the shared folder and then going to your Google Site to insert a link or attach the file. Why take 2 steps when you can do it in one! Something so simple can end up saving a teacher a lot of time in the long run. Share the tip with your friends and co-workers.