Looking at Ofsted ratings and academy status might help when choosing a school for your child because there's little else to go on. When your child is already at the school, you can look more closely at whether the school suits them, eg are they making progress, are they receiving the right support, do they have good relationships with staff and students. The Ofsted rating changing doesn't change any of those things. The school is no worse today than it was yesterday.
When I first taught in this country, I taught at a RI school converting to an academy. It was also located in a fairly deprived neighbourhood and the other nearby school had been shut down after its Ofsted. There were difficulties but there was an onsite behaviour management team, counselors, strong pastoral programme, an emphasis on helping individual students do their best.
I now teach in a "naice" oversubscribed school. It is an academy but nothing changed. Good but outstanding in some areas. Top local state school for GCSE and A-level results. But it's not so high on the league tables when you look at Progress. Very little support from SLT for behaviour management. Hardworking SENCo and pastoral lead, but you get the feeling that unless the student is D/C borderline (eg will affect league tables) the management don't car.e
My DC are far to young to be thinking about secondary admissions, but currently I'd rather DD went to a school like the first one. And sometimes I secretly wish the school I teach at now would get a bad Ofsted or a low-achieving cohort so that management would have to sort out the issues!