There is an ongoing debate about public charter schools and skimming that goes something like this:

“Studies such as CREDO and other high-quality analyses show that charter schools in some cities are substantially outpacing other public schools.”

“Well of course they are, they’re skimming the most motivated families. It’s not the schools.”

This back and forth is usually reported in the media as two distinct takes on the same issue. In fact, both these things are true at the same time.

Let’s start with the “skimming.” Most charter schools don’t skim their students (in fact they’re not allowed to, it’s traditional public magnets and theme schools that are able to use selective admissions standards) and many charters focus on the lowest-income students. But, there are certainly cases where signals are sent, especially in regard to special education students, and many charters have distinct themes or norms that do not appeal to all parents. (As charter schools grow in many cities addressing issues like special education will become unavoidable. We don’t expect each public school to educate every student, districts do this by aggregating resources, but we should expect the charter sector as a whole to equitably serve the most challenging students once that sector reaches a certain size). Some students also struggle once they enroll in a specific charter.

But more to the point, in an environment where assigned schools and choice schools operate side-by-side it’s not surprising that it’s more motivated parents exercising choice right now. So the schools are not “skimming” but there is almost certainly some selection effect.

But that’s where it gets interesting. Because there are more parents who want to enroll their students in charters than there are seats available researchers have been able to compare students to applied to over-subscribed charters and didn’t get in through the random admissions lottery with those who did get a seat. In other words, the scarcity of seats in the most in-demand charters creates a natural experimental and control group of students. And the results show that even among these students, with similarly motivated parents and only the luck of the draw separating them, high-performing charter schools outperform. Other research, for instance the methods used by CREDO, bolster this finding. So the good schools are doing something that matters – in some cases a lot –  on top of any advantage they might gain from the students who come their way.

So put plainly, yes selection and skimming matters, but despite that, the evidence shows that some charters have a substantial positive effect that is something educators and policymakers should seek to learn about and replicate rather than dismiss out of hand based on a misunderstanding of what’s happening.

What makes for a good sector of charter schools? Fordham is hosting a forum on different ideas about that.

Update: Below commenter David B. makes an important point about how generalizable the results from over-subscribed (and often “no excuses”) charters are. He’s right and there is a lot to learn about the broader implications. But unfortunately, rather than a thoughtful conversation about how to improve customization within public education and figure out how to provide better options for all students, the charter debate has turned into a team sport where each side just has a rooting interest.