Good schools in good areas tend to remain good.
Newly good schools in more challenging areas tend to be the work of one or two inspirational people, with cash behind them. Once they move on and up,the schools stand a real risk of dropping back.
This is why OFSTED, cashed strapped as they are, tend to focus on more struggling schools. Poor OFTEDS can equal cash.
Parents who do the research, pay the house price premium, comb the results stats, talk to the local primary heads, know the parents of kids currently at the school, see those kids walking home every evening, attend several prospective pupils open events, question the kids we meet, see the local news reports about what kids are getting up to at the school, OR have happy children at the school, performing at least to their innate ability, if not beyond....tend not to need yearly OFSTEDS to assess the school.
Also, if I'm honest, we're not stupid. Many of us have seen remarkably average 'local' schools getting 'great' OFSTEDs - where the parents of pupils actually attending go 'Outstanding? Rilly?'
OFSTED has its place, but it's been ridiculously politicised.