Charter schools are authorized by an external body, called an authorizer or sponsor, which is supposed to hold the schools accountable for their performance. Sometimes that authorizer is a local school district or the state Board of Education; sometimes it’s a state or private university, a nonprofit entity, or a district from another part of the state. (Laws on who can authorize charter schools vary from state to state.)
Some states allow or require charter schools to have a much closer relationship with the local school district. For instance, in Massachusetts “Horace Mann” charters must be approved by the local school board and staffed by unionized teachers who are generally covered by that district’s collective bargaining agreement. (“Commonwealth” charters are much more common in Massachusetts and are not subject to those requirements.)
Sanders said Sunday that he opposes “privately controlled” charters, which may suggest that the authorizing body or relationship with the local school board is an important distinction. But even if that’s what he was referring to, it’s not clear what he means. Perhaps Sanders only backs charters overseen by the local district; maybe he supports charters overseen by any public entity. We just don’t know.