Students should follow these instructions on how to successfully log out of Google Drive when they have logged in when using a SHARED iPad:
In the Google Drive app:
Tap on the profile icon (top right)
Choose "manage accounts on this device"
choose "remove from this device" for the account you wish to remove (all accounts should be removed for the next user).
Then, the student should open Safari and:
Tap on the profile icon (top right)
choose "sign out."
After completing all of these steps, the student should be logged out of the Google Drive app, as well as their Google account through Safari. The iPad is then ready for the next user.