When you operate as a QFI etc, you need a lawyer purched on your shoulder.
DUTY OF CARE is the magic word.
The more the student is considered to be a loose cannon, the lower his overall standard, the greater the duty of care is required of you as his instructor.
Can you justify every action you have taken if it ever got to court? Is there anything written in the student's file which the lawyers would feel incriminating; a god send to the other side?
What does your gut feeling tell you?
Any chinks in the armour could prove to be very expenses in damages.
Take a great deal of care my friends.