Charters are explicitly reductions in institutional legal accountability, and unlike public (charter or not) schools, the chief decision makers so released from accountability with private schools are not accountable by election, either.
Yes, and it's difficult to get information from charter schools because they are not subject to the same reporting that public schools are. This makes it easy for people take advantage of their opaqueness.
Harper’s recently ran a pretty good piece on the matter, if anyone is interested in a longer-form skeptical perspective on charter schools and their lack of accountability:
Charter schools are accountable to the parents. If the parents do not like the performance of a charter school, they can pull their kids out of it, and put them in their neighborhood public school.