Cackademies generate a whole new level of teacher churn, which is generally pretty high anyway.
The first couple of years have always winnowed out lots of new teachers who struggle in the classroom, or who quite sensibly decide early on that it's an awful lot more work than they fancy committing to for the next 40 years.
More recently, you've got a huge trend of experienced teachers being neatly levered out in certain Academies because they are both expensive & not terribly biddable/bullyable.
Then you've got an NQT-drain because the same Academies have a nasty tendency to recruit lovely cheap NQTs & then find excuses to deny pay progression to keep the costs down. The confident ones realise they're being played & bugger off, whilst the more easily cowed struggle on a little longer, until being constantly told they're a bit below par sees them off too.
It's grim. I love teaching, plus I'm naturally bloody minded, so have a cast iron intention that there'll come a day when I'm still in education & Michael Gove is not, but I can't pretend I don't feel like I'm in the band on the Titanic.