In order: No, it's not that simple. Might be nice if your deputy head and HoD gave you some support, to which you are entitled, instead of sitting in judgement of you. And remember, the school grade is unsatisfactory. In my opinion, that means the management is unsatisfactory and is therefore not fit to sit in judgement of anyone else. No, why should you? Yes, and make sure it is someone who has had the relevant training.