Guided Access is an accessibility feature that locks the iPad into using a single app and could also disable certain features in that app. When enabled, it prompts you to enter a passcode which will be used to unlock it - this is different from the passcode which unlocks the iPad after a period of inactivity (which is not enabled on Student iPads). Although you can clear the normal passcode from Workspace ONE, you cannot clear the Guided Access passcode from Workspace ONE. If you enable Guided Access, you cannot do a normal reboot of the iPad, but you can do a hard reset, by holding down the power and home buttons for five seconds. However, if you do a hard reset, when it reboots, it will automatically re-enable Guided Access.
If the person who enabled Guided Access forgets the passcode, the only option we have found is to do a Device Wipe or a Restore.
I also looked into trying to completely disable the Guided Access feature using a Policy in Workspace ONE, but apparently this is not supported.