What does the phrase "charter school" convey? A common working definition is an "independently operated public school of choice, freed from regulations but accountable for results." Yet all that such formulations of the charter school concept address are matters of structure, governance, and accountability. They say nothing about what sort of education is occurring inside the schools themselves. What is their curriculum? Their pedagogy? Their theory of learning?

Discussions of chartering seldom get close to such matters. But the essence of a charter school is supposed to be its differentness from other schools, at least other schools in its vicinity. If it's not different, why attend it? Which leads to the question, How is it different? What makes it tick as an educational institution?

Why these questions rarely get asked, much less addressed, has two answers. First, people are apt to read too much into the "charter" label itself, somehow viewing it as a school's key attribute rather than merely a license to operate under certain conditions. It's akin to using the word "boy" to describe a kind of person, or "bird" to characterize an animal. Yes, it tells you something, mainly about what the creature is not - not a girl, not a mollusk or amphibian. But it doesn't tell you much. The differences among boys - big and little, strong and weak, black and white and brown, toddler and quarterback, law-abiding and delinquent - are vast, and in many ways more consequential than the difference between boy and girl. "Boy" just doesn't tell you a heckuva lot. Neither does "charter school." The fact that a school operates under a charter may, indeed, be the least important thing about it.

Second, and at the opposite extreme, some people think every charter school is sui generis. They see a corpus of 3,500-plus such schools operating in America and believe them to be so unbelievably diverse that each is best seen as a unique educational institution. If you follow that reasoning, you would not be disposed to generalize, save to note that they all have charters.

Both views are wrong. The array of educational institutions that has come to wear the charter label these past 15 years features a number of distinct subsets or types. They're not just "birds." Edison schools are different from Paideia schools; dropout-recovery schools differ from primary schools as "virtual" schools differ from the brick-and-mortar kind; and so forth.

But neither are we looking at 3,500 categories. This ice cream parlor does not contain infinite flavors. It has just a few dozen. The forty-odd KIPP academies have a lot in common with each other, as do, say, the "Core Knowledge" charter schools. Knowing that a school belongs to one of those groupings tells you a lot about it.

Somewhere between an undifferentiated mass of 3,500 "charter schools," and 3,500 unique institutions wholly lacking in subcategories, my Fordham colleagues and I reasoned, there was a "typology" waiting to be created. A reasonably analytic, manageable number of categories or flavors of charter schools. With a typology in hand, we further reasoned, one could learn still more. How many are there of which sorts of schools, for example? Do they serve different populations? Do they tend to be bigger or smaller? And then - the $64,000 question - is there any difference in their academic performance, any difference that corresponds to (or is even caused by) their distinctive characteristics?

This was unknown territory but well worth exploring. So we asked Dick Carpenter of the University of Colorado at Colorado Springs to work on it. Now a professor and scholar, Carpenter once served as principal of a K-8 charter school - an experience that heightened his interest in this study.

He's completed the first half of it, enshrined in a Fordham Institute study released today.  You can find it on the web, here. The study, based on a careful sorting of 1,182 charter schools, presents a cogent typology. The charter schools he examined and categorized represent 87 percent of all those operating in 2001-2002 in the five states (Arizona, California, Florida, Michigan, and Texas) that then accounted for the lion's share of U.S. charter schools.

Carpenter first sorted them into 55 categories - more flavors, even, than Baskin & Robbins - then grouped them into ten larger groupings. He shows how many schools are in each and provides fascinating information on the kinds of kids they enroll, how big they are, etc.

It's a bona fide charter school typology, something that charter watchers have never had before. Moreover, it's pretty interesting. I was surprised to see, for example, that "progressive" schools outnumber "traditional" schools - but that both are surpassed by what Carpenter calls "general" schools, i.e. those with no distinctive curricular or pedagogical emphasis. I was less surprised to see the large percentages of charter pupils in every category who are poor and minority, but it is interesting that low-income pupils are somewhat less common in "progressive" and "alternative delivery" schools.

The 55-category version has some tantalizing tidbits, too, such as that "Core Knowledge" accounts for the second largest category of "traditional" schools (after generic "back to basics") and Montessori is the largest category under "progressive." 

To be sure, the charter world is changing. There are lots more Edison schools today, for instance, than three years ago, and dozens of KIPP Academies (not even a discernible category in 2001-2002). The number of "home study" schools has decreased while "virtual" charter schools have blossomed in many states.

So it's not 100 percent up to date. But few typologies are. We needed a field guide to charter schools, and now we have one. Such a typology, tweaked from time to time, is a valuable contribution to our understanding of charter schools and our capacity to study them.

Next on the agenda for Carpenter and this project: a valiant effort to determine whether student achievement in charter schools corresponds to type. Stand by, please, and in the fullness of time we will share what we learn.  

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