At least that’s how they started. Somewhere along the way, however, the charter school movement—buoyed by a few high-profile foundations and corporate leaders—strayed from living laboratories of practice for the benefit of public education to private schools at public expense. They suddenly became competitive “schools of choice” aiming to supplant public schools rather than support them. Conveniently, they retained the ability to dodge public school restrictions, primarily the pesky requirement to educate all students, by virtue of transfer provisions and an application process that requires, at the least, an attitude at home that reinforces the importance of education. What of the students who don’t have that advantage? They don’t appear in the film. They don’t appear in charter schools. But they do appear in the nation’s public schools. And public school educators are accountable to move the needle on their achievement each day.

A 2009 study of Boston charter schools, for instance, revealed that less than 50 percent of students who begin as freshmen go on to graduate from that school four years later. Those students typically transfer to and graduate from their local public school. Remove that safety net, however, and Boston charter schools meet the criteria of “dropout factories.” I’m sure great things are happening with the performance of the students who remain, but so high an attrition rate does not elicit a Eureka!

I suppose we should be grateful that Waiting for Superman is broadening the conversation about public schools throughout the nation. We need an honest, productive conversation about the standards and expectations for student performance. We need an honest, productive conversation about how schools should be organized and resourced to drive the achievement we expect. But such conversations require a more genuine set of inputs than Superman provides. And with public education having to shout over a divisive charter agenda supported by unprecedented media, money, and policy, you have to wonder if the conversation will be as balanced as we need it to be to see any real large-scale educational improvement.

Gerald N. Tirozzi is the executive director of the National Association of Secondary School Principals.