Charter opponents have long claimed that charter schools siphon resources away from the traditional public school system. The ideological motivation for this line of reasoning is clear when touted by teachers unions and their friends: i.e., calling charters parasitic unless they conform to traditional school practices, including mandatory unionization, makes that bias obvious.
But what impact do charter schools actually have on traditional public schools and the students who remain there? Are such loaded accusations deserved? Or might the presence of charters improve student outcomes through competition or as effective charter practices spill over into district schools?
Recent research from Temple University professor Sarah Cordes sheds needed light on this question. Cordes examined the impact of charter schools in close proximity to, or even co-located with, traditional public schools (TPS) in New York City over a fourteen-year time span. Her analysis departed from previous research examining charter effects at the district level or across a much-wider radius (up to 10 miles, versus Cordes’ one-mile radius), and was also the first peer-reviewed study of the academic impacts of co-location. Data came from 900,000 students in grades three through five. The study design (a difference-in-differences model) was similar to past research on charter effects, but Cordes added new statistical checks to avoid conflating possible student composition changes at the schools with performance gains. The study also examined school-level factors not previously well-studied that could explain charter effects on TPS performance.
So what did she find? Exposure to charter schools significantly increased student performance at nearby traditional public schools. The effects increased with proximity to the closest charter school; students at traditional publics schools co-located with charters experienced the greatest positive impacts. Small impacts were observed for schools close to charters but began dissipating when a half mile or more away. Students at traditional public schools also experienced reductions in grade retention when co-located with or close to a charter, as well as small positive effects on their attendance. As for the impact on student subgroups, the most positive impacts of charter exposure (for students in nearby traditional public schools) occurred for poor students and those eligible for special education services. There was no significant impact for public schools that co-located with another public school: In other words, it was the shared space with a charter that made the difference.
The study also examined possible school-level reasons for positive charter effects, using parent and teacher survey data. Several plausible explanations emerged. Traditional public schools co-located or nearest to charters experienced improved student and parent engagement, higher expectations for students, and improved perceptions of safety and school cleanliness—any or all of which could have translated to improved student performance. It’s also possible that those public schools’ increased per-pupil expenditures (PPE) of two to nine percent—resulting from student attrition (more dollars spread over fewer students)—helped have a positive impact.
More work remains on digging into the reasons why traditional public school students might experience positive effects from nearby charters so that others might emulate such improvements. Most importantly, the study confirms that charter schools can have a positive competitive effect on nearby public schools. This confirms previous research showing that not only charters, but other forms of choice like vouchers, can impact traditional public schools for the good. More districts—especially those with excess capacity in their school facilities—should consider co-location with charters for the mutual benefit of all students and families.
Sarah A. Cordes, “In Pursuit of the Common Good: The Spillover Effects of Charter Schools on Public School Students in New York City,” Education Finance and Policy (July 2017).
