(Source: U.S. Department of Education, National Center for Education Statistics)

 Charter school advocates commonly say that caps on the growth of these public schools in some states are preventing the opening of some high-quality schools. Is this actually true? Matthew Di Carlo, senior fellow at the Washington D.C.-based non-profit Albert Shanker Institute, looks into this. The following post originally appeared on the institute’s blog.

By Matthew Di Carlo

Charter school “caps” are state-imposed limits on the size or growth of charter sectors. Currently, around 25 states set caps on schools or enrollment, with wide variation in terms of specifics: Some states simply set a cap on the number of schools (or charters in force); others limit annual growth; and still others specify caps on both growth and size (there are also a few places that cap proportional spending, coverage by individual operators and other dimensions).

 A great many charter school supporters strongly support the lifting of these restrictions, arguing that they prevent the opening of high-quality schools. This is, of course, an oversimplification at best, as lifting caps could just as easily lead to the proliferation of the many unsuccessful charters. If the charter school experiment has taught us anything, it’s that these schools are anything but sure bets, and that even includes the tiny handful of highly successful models such as KIPP.*

 Overall, the only direct impact of charter caps is to limit the potential size or growth of a state’s charter school sector. Assessing their implications for quality, on the other hand, is complicated, and there is every reason to believe that the impact of caps, and thus the basis of arguments for lifting them, varies by context – including the size and quality of states’ current sectors, as well as the criteria by which low-performing charters are closed and new ones are authorized. 

 Most obviously, in a few states, the cap has been set much higher than the actual number of schools. For instance, until recently, the number of charters in California was so far below the cap (1,250) that it’s tough to believe lifting the restriction would have had much of an impact.**

 The well-known CREDO charter school study took a quick look at this association, and found that charters tend to do slightly worse in states with caps, as well as in states in which the charter sector was at 90 percent of the cap (e.g., approaching the limit).

 But this, of course, is just a simple association, one based on a small sample of 15-20 states, and it does not necessarily reflect causality. For example, it’s quite plausible that the absence of caps is a symptom, rather than a cause, of strong authorization practices and a supportive policy environment more generally.

 States with these conditions may be less likely to impose caps, and it’s the former and not the latter that probably shapes aggregate performance. Thus, lifting caps in states without effective authorization, etc., could hurt more than it would help, since it would merely permit more low-performing charters to open.***

 On a related note, there is an argument that caps might actually serve as an incentive for the kind of “close the bad charters, scale up proven models” approach that charter supporters so frequently espouse. In other words, one could hope that states with relatively low caps — and/or those approaching their cap numbers — might be more vigilant about quality control in the authorization of new ones (and, perhaps, the closing of low-performers). If there’s no cap on enrollment or growth, there might be less emphasis on quality assurance and more on unchecked proliferation (or vice-versa).

 This viewpoint is particularly relevant given two brutal realities. First, the closure of charters due to low academic performance is something of a rarity, though there is tentative evidence it may be on the upswing. (Side note: I am personally very uncomfortable with closure as an education strategy, though that’s a topic for a different time.)

 Second, as mentioned above, only a relatively tiny handful of charter models get consistently good results, and they tend to be those that employ interventions such as drastic increases in school time and tutoring. These schools’ approaches require extensive investment (both up front and on an ongoing basis), for which they must rely on private donations. And, as always, it’s unclear how policies such as 8-9 hour days and rigid discipline practices would work on a larger scale. This may be why it’s often the smaller sectors that stand apart in terms of performance.****

 In other words, “bad” charters rarely get shut down and “good” charters are scarce, expensive, and difficult to scale up – a circumstance that is widely acknowledged by charter supporters and opponents alike (even the most well-established CMOs vary widely in their effects, and have trouble expanding).

 Perhaps this is due in part to the fact that many states provide little incentive or clear guidelines for closing and/or insufficient quality control in authorizing new schools. In these places, it’s possible that caps are the only thing preventing widespread proliferation of schools that are usually no better – and often worse – than the regular public schools they supplant.

 In New York, for example, the cap was quite low for many years (100 charters). Without question, some schools, perhaps effective schools, might have opened but for this restriction. On the other hand, it’s also possible that this cap was part of the reason why New York City, in which most of the state’s charters are located, is one of the few places where these schools get stronger than average results. Throughout the 2000’s, despite the city’s massive enrollment, its charter sector expanded very slowly, with only a handful of new schools opening every year. These were carefully chosen, well-funded and methodically planned. The cap might have had something to do with this deliberate approach.

 (The same basic speculation might be made about Boston, also among the very few single locations where the charter sector as a whole seems to do quite well. As of 2009-10, Massachusetts allowed only 120 charters, and, once again, it’s possible that this restriction reflected and/or contributed to a slower, more careful expansion process.)

 So, once again, whether caps exert a positive or negative influence (or some mix of both, or neither) likely varies by context. In states where authorization (and deauthorization) policies are very strong, caps might indeed serve as a hindrance, since quality assurance mechanisms already operate via other formal channels.

 Where authorization practices are weak,  and/or large proportions of currently operating schools are low-performing, however, states should think three times before rushing forward with a plan to lift caps, and charter advocates should do the same.


 * KIPP has a well-earned reputation for success, one that should not be minimized. However, in contrast with some of the overblown rhetoric (e.g., “cracked the code”), it’s worth noting that the 2010 report often used as evidence of KIPP’s test-based results finds that about one in four of these (22 middle) schools are not significantly better than the schools to which they’re compared (though overall estimated effects are strong, very few do significantly worse and even the non-significant effect estimates tend to be positive). KIPP seems to be a very good bet, at least at their current scale, but not a sure one.

 ** It’s also possible that caps may serve a “signaling” function, which discourages operators from opening up shop in states that impose them. If so, then caps might limit growth somewhat even if charter sectors are nowhere near reaching their limits.

 *** Some charter supporters also argue that the proliferation of charter schools carries benefits for all nearby schools, in the form of improvements spurred on by increased competition. According to this argument, lifting a cap might be a good thing, even if the new charters that open as a result aren’t particularly high-performing, since their mere presence will foster market-based competition among neighboring schools. There is some research basis for this claim, but it is still quite limited, and much of focuses on vouchers. Also, it’s not clear how these effects would play out in a situation where a cap was deliberately lifted to permit expansion, as that might alter the kinds of schools that opened up and their market effects.

 **** Charter supporters would no doubt point to New Orleans as an exception. In a sense, that’s fair enough, and please see our post on NOLA charters.

 The views expressed in this post do not necessarily reflect the views of the Albert Shanker Institute, its officers, board members, or any related entity or organization.