An evaluation of the charter program in a state needs to begin with an examination of the law. The charter program in a state is not, in other words, simply an adding-up of how well in the aggregate the charter schools are working. If the law does not work at all there will not be schools at all. If no schools are being created the law is clearly failing. But the evaluation should not stop there.
Success is more than just schools-appearing, however.
To be 'working' the program needs to produce schools also for regular students. Only if schools appear that are attractive to families the districts want to keep will districts respond with changes and improvements in their own programs. Quality is important, along with quantity. In most states where schools are appearing the Legislature has made it possible for more than one public body to be offering public education in the community. So in the important states there will be fascinating questions about the different behavior of the different kinds of sponsors.