A recent study by researchers at Michigan State University found that students attending charter public schools were more likely to graduate, and then matriculate at college, than their non-charter counterparts. The study used data from Florida and Ohio, plus data from five major cities where charter schools are present.
I sit on the board of Black River Public School, an innovative K-12 charter school here in Michigan. There's no doubt in my mind that Black River offers an excellent program that is available free of charge (just like any other public school) to any student in West Michigan who wants to attend.
More precisely, the school welcomes any student who wants to attend it, and who can also win a spot in our school's annual lottery. When the price of something is zero dollars (as is the case with charter schools), and the quantity demanded exceeds the quantity supplied, then other rationing schemes must be used. And charters traditionally have used lotteries, since other potential rationing schemes seem patently unfair.
But let me return to the study's conclusion: that students attending charter schools are more likely to walk through commencement exercises, and then attend college. Again, I'm confident most charters have outstanding programs. In fact, if a charter school is rotten, the state and the school's chartering organization will shut it down. In fact, Michigan's charter authorizers have closed 38 charter public schools since the Michigan public school academy law was enacted in 1993.
In studies like this one, though, there is a potential for selection bias. What I mean is that since the scholars at MSU were studying the choices that students have made (whether or not to go to college), after they have already made them, it's almost impossible to know whether there is a treatment effect of attending a charter or not.
On one hand, maybe attending a charter makes students more likely to attend college. That is, maybe it really is something about the charter experience that makes the difference.
But on the other hand, perhaps the sorts of students who end up in charter schools are already more inclined to attend college--even before they darken the door of the charter.
And it's not difficult to imagine how this might happen. Normally, students (and their parents, of course) explore charter schools as an alternative option from the traditional public school. So merely by exploring charters as an educational option, students and their parents reveal that education is important to them. And perhaps children from those families--where education is viewed as important already--are exactly the sorts of children who apply to attend college regardless.
So is there a treatment effect? Does attending a charter increase the likelihood that a given student will attend college? Or does a charter simply address the needs of students who probably plan to go to college anyway? Selection bias can be pesky indeed when trying to isolate a treatment effect.