The advent and spread of charter schools—publically funded schools that operate independent of the surrounding school district—have raised important questions, including why the performance of charter schools themselves varies. But in public debate, the most prominent policy question related to charters hinges less on their effectiveness and more on their effect on so-called traditional public schools. Traditional public schools, significantly, remain those that a large majority of a school district’s students will continue to attend—thus the impact of charters on these schools is of obvious importance.
Competing schools of thought have emerged in response to this question. Those who are optimistic about charters as a leading edge of systemic reform argue that the methods and structure of charters that prove successful will, in turn, influence practice in non-charter schools—to the benefit of school systems at large. Such effects may be magnified because traditional public schools will have to compete with charter schools for students—and the financial support that comes with them. Opponents of charters, in contrast, focus pessimistically on the possibility that the more able students—and their good example—will be diverted to charters, along with physical and financial resources.
These two schools of thought have led, not surprisingly, to an emerging body of empirical research. Such work has broadly demonstrated that neither side of this debate is entirely correct. A fair reading of the empirical research is that the introduction of charter schools—and the resulting competition for students through school choice programs—has either a small, positive effect or no discernible effect (though not a negative one) on student achievement in local traditional public schools.1
This paper adds to the charter school–related research by examining another dimension of the relationship between charters and traditional public schools. It seeks to determine whether charter schools could influence public schools, for better or worse, in a particular situation common in some cities: where charter schools share buildings, or are “colocated,” with traditional public schools. (In colocations each school is assigned a segment of classrooms and hallways, while major amenities such as gyms, cafeterias, and libraries are shared.) Charter school colocations are found in urban school districts across the nation: Chicago, Denver, Boston, Milwaukee, and several large districts in California use the practice.
Colocation is perhaps most widespread and controversial in New York City, where the high price of real estate makes such colocations common. Indeed, colocations of public schools generally—not just those involving charter schools—are a distinctive feature of the New York City schools. During the Bloomberg administration from 2002 to 2012, the number of public schools increased from fewer than 1,200 to more than 1,800. This increase was due to the rapid growth of the city’s charter sector—which increased from 17 schools in 2002 to 183 in 2013—and a general strategy of dividing large schools into smaller, theme-based academies. Today, 1,150 (63 percent) of the city’s 1,818 public schools are colocated. Of these 1,150 colocated schools, 115 are charter schools. More than two-dozen approved charter colocations have been approved for the 2014-15 school year but are now being reviewed by the de Blasio administration and are the subject of a lawsuit brought by the teachers union.2
As in the broader debate, competition theories have been advanced as to the effects of such situations. Those who are concerned about the spread of charters fear that they might prove intrusive and compete for scarce physical and temporal resources; others hope that charters might serve as positive examples for their public school neighbors. Though colocation among traditional public schools is common and often goes without comment, new charter school colocations in New York City often cause controversy.
That colocations lead to operating changes in the traditional public schools that are already operating in a facility seems clear. But such changes should only be worrisome from a policy perspective if they lead to lower student performance in the traditional public schools that are required to share facilities.
Do colocations affect student achievement in traditional public schools already operating in a facility? Do colocations with charter schools have a particular effect on public school effectiveness? These important questions have yet to be addressed in any empirical research of which I am aware.
In this paper, I use data following the test-score performance of individual New York City students over a period of five years to assess whether colocations affect student achievement in traditional public schools. Essentially, the empirical model compares academic growth in a traditional public school before and after the introduction of a colocation, or as the magnitude of the colocation changes, holding constant everything about the school that does not change over time.
I find no evidence that colocations—whether with charter schools or with traditional public schools—in New York City have any discernible impact (positive or negative) on student achievement in a traditional public school. This result is consistent across various measures for the existence and magnitude of colocation.
It is certainly possible that colocation arrangements produce discomfort for all parties. (There are often difficulties scheduling the use of common spaces such as cafeterias, auditoriums, gyms, etc.) However, any inconveniences due to colocations do not appear to manifest in lower student learning in receiving traditional public schools. Thus, the evidence suggests that policymakers considering colocations need not weigh the potential benefits for students who would attend a charter school against reductions in the performance of students attending a traditional public school that is required to share facilities with the charter.