With class at McKinley High School about to go back in session -- the full cast of "Glee" got together for a Season 2 photo shoot ... and we got our hands on some behind-the-scenes footage!
The cast members were full of excitement as they clowned around for the day at Smashbox Studios in L.A. -- check out all the candid moments!
Season 2 of "Glee" starts September 21.
