The solution for the school head is easy, send the child home at the end of the day with a letter to the parents telling them the school only teaches children. Suggesting to them that as the child now thinks it is a dog and a dog trainer is the most suitable place for the child to go to, let the parents sort them out, if the child does have social and emotional needs it is up to them to arrange it. Schools with their budgets cut and work overload have neither the time , money or staff to deal with it. The child would always be welcome to attend the school again when they identify as a child.