Tortoise,
The correlation between FSM and Ofsted rating is statistical, not predictive - I know very 'naice' primaries, in particular, where low FSM was no protection from Special Measures, and of course there will be schools with high FSM - not the very highest, but higher than average - that get good and Outstanding Ofsted ratings (and then tend to see their %FSM dropping as MC parents fight to get their children into them).
So perhaps it would be clearer to say that 'schools with very low %FSM are statistically much more likely to be Outstanding than schools with very high %FSM (and also, statistically, very likely to be selective)'. Schools with middling levels of FSM, like Skinners', are more mixed in terms of Ofsted.