There is no way for the headset to know who is wearing it, but it is important that each user be aware of the health and safety information.
Most likely the battery in the controller needs to be replaced. If that doesn't work, you can try to re-pair the controller to the headset.
The Oculus Guardian can be reset from the headset. Make sure the headset is set for RoomScale Guardian. All FreeRangeXR VR experiences assume a 10ftx10ft (3mx3m) space available. Also check that the student starts in the center of that square.
Help the student physically move to the center of your space, then press and hold the Oculus button until the area re-aligns itself. If that doesn't work, you should quit the app, and launch again. Hint: Make sure students start the app at the center of your space, especially after another student has done a lesson.
Most of the time the gear will respawn, but it is possible to discard gear outside the play area. If that happens the student will need to exit the lesson and restart.