It sounds like some over reaction on the Teachers part on writing letters they should be able to deal with it them selves and if she wont sit down at school its up to them,to sort it out..A lot of bright children want to have things their own way ,sounds very normal to me,does she have plenty to do if children get bored they act up, has the school ,and your selves at home, activities and Games and sports, does Dad get involved with her and get some physical Fun going very often they love to be active , does her school have any after school Gym or dancing clubs .