i remember when i was in nursery there was some teenage dude from some other school that came in to "help" the kids

very disturbingly, he started giving the "chinese twist" (grabbing the arm of the little children and twisting it in opposite directions with both hands sharply) and insisted that it was necessary and 'healthy'

every now and then i remember this experience and fear that this boy went on to continue doing these things and worse later on