They also have a problem with the way that Ofsted went about things but I don't know why.
This does happen when Ofsted arrives with a particular 'agenda' - for this school, it will have been safeguarding, poor documentation in key areas and progress of particular groups (I imagine, though, that the use of 'extended study leave' to avoid exclusions, poor teaching; weak governance and poor behaviour were things that arose during the inspection) - that the school can feel that their own narrative about the school is brushed aside.
In this case, Ofsted's concerns were so much 'about the heart of education', and the school's so trivial (extracurricular provision) or outdated (headline results) by comparison that I don't think the school is particularly justified in its complaint.
However, I have known other schools where Ofsted has arrived with a narrative about e.g. progress of particular groups, and have brushed aside (sometimes to the point of abuse of the head and other teachers) the school's points about very significant non-school factors that affect those groups (e.g. homelessness; entrenched worklessness in the community; imprisonment etc etc etc), and that has been very difficult for the schools concerned.
So I'm not saying that Ofsted DOESN'T get their approach wrong, just that the school protesting about Ofsted's methodology when the weaknesses identified are so severe, so worrying, and so widespread (a Safeguarding -based fail where all other areas are Good is one thing, but this report has nothing above Requires Improvement) feels like they just haven't acknowledged the fact the school has a genuine problem.