The IBO report on NYCDOE schools was just released - you can see it here in PDF.
I'm starting to pore through it now, but here's one stat that got my attention (though given the Bloomberg policies of hiring lots of people with little-to-no education experience whatsoever to work as "team leaders", it's not a surprise):
In 2000-2001, principals in DOE schools averaged 14.0 years as a teacher.
In 2012-2013, principals in DOE schools averaged 9.1 years.
That's nearly a five year decrease in experience working as a teacher.
And you can see from the trajectory that the teaching experience of principals has gone done EVERY year since 2000.
You've still got some principals in DOE schools who taught for a good period of time before becoming administrators.
But you've also got a lot who have little experience as teachers.
Because what can be a better deal than having somebody with little-to-no teaching experience leading a school as principal?