I hate to say it, but the parents have a responsibility in this too.
You don't leave your child with another adult unsupervised. Period. I'm not saying you hold their hand or don't let the instructor do their job. It's their school and they should be allowed to discipline accordingly.
But, i'll be ****ed if I leave them unattended with someone I only know on a professional level. Hell, I only let my mother in law and my mother watch my kids. I may be a little paranoid after having read all the PC's to judges for so long that involved these kinds of charges.
It is better to have less thunder in the mouth and more lightning in the hand. - Apache Proverb