Consider that charter schools and private schools in NY may not be indicative of the growing trend nationwide. I have never heard of a charter school opening in a closed down public school locally.
I have seen the differences in private vs public education, and they are quite significant.
The problem that politicians have with education is that they try to quantify success with hard data and metrics much like you do in the private sector. The translation does not apply. How do you judge a teacher's efficacy? Their students' grades? Who assigns those grades again?
Additionally I think the push to 'mainstream' every child is a problem. Kids that may benefit from more one on one time become disruptive to a class that does not need the added supervision or distraction.