Swinging on a chair can cause a lot of damage to a child, if the chair goes over. Would your daughter have preferred her son with concussion, a broken limb or even worse, or would she rather her son have a telling off by a concerned teacher who was trying to do her job, with your GS's safety and best interests at heart? Standing for a couple of hours, to teach him a lesson, isn't going to harm in. Hopefully, it will deter him from continuing to do it. If it were my child, I would've told him that the teacher did the right thing, and he should listen to her in future! Parents these days all seem to think that their children are little angels. I've worked with children in the past, and they are far from it!