Education Secretary Betsy DeVos caught a lot of heat after she appeared unable to refute CBS News reporter Lesley Stahl's assertion that Michigan's public schools worsened after the state expanded charter school funding during a recent interview on “60 Minutes.”

While some knocked DeVos' knowledge of the issue, the polarizing interview prompted the question of whether charter schools help or hurt neighboring public schools' academic performance. The answer, however, is more complex than the interview may have indicated.

What Are Charter Schools?

According to the Education Department, charter schools are entities that receive public funding but operate with greater autonomy than traditional public schools. Charter schools often have few or no zoning limitations due to the fact that they don't belong to any particular school district.

Their structure can vary by state and can focus on particular subjects — like science, technology, engineering, and math (STEM) — and can even reside in the same building as a traditional public school. They often belong to very small networks within a particular state.

Proponents tout charter schools as offering parents more choice over where their children can receive an education, as well as their alleged ability to improve student performance.

Nina Rees, CEO of the National Alliance for Public Charter Schools, declared last year that the debate over charter schools was “over” and that charter schools were unequivocally better than their traditional counterparts.

She and Howard Fuller, distinguished professor of education at Marquette University, cited charter schools' prominence at the top of national rankings, as well as a Stanford University study showing that Philadelphia charter schools benefited students of color.

But opponents at the National Education Association (NEA) argue that charter schools lack accountability and aren't held to the same standards as other public schools. Charter schools, the NEA argues, create unequal education systems that deprive students of color of a high-quality public education system.

Although DeVos appeared to favor charter schools during her “60 Minutes” interview, she also acknowledged their limitations.

During a speech last year, she told the National Alliance for Public Charter Schools that charter schools might not meet the needs of every student.

“Charters alone are not sufficient. Private schools alone are not sufficient. Neither are traditional schools,” DeVos said in her prepared remarks. "And that's OK.

“Let's humbly admit this fact and recognize that no top-down, one-size-fits-all approach will ever help us achieve the goal of giving every child an equal opportunity for a world-class education,” she added.

Arguments For and Against Charter School Funding 

During her interview, DeVos pointed to evidence claiming that Florida's traditional public schools saw better performance than the state-funded charter schools.

Charter school proponents argue that their introduction creates competition that forces traditional public schools to find ways to improve academic performance.

A 2016 study supported this theory by reviewing data for New York City's education system from the 1996-97 academic year to the 2009-10 academic year.

Sarah A. Cordes, the study's author, said her results suggested “that charter schools have small positive spillovers on public school students.”

Similarly, a 2006 study found a connection between modestly higher math scores at Florida's traditional public schools and their proximity to charter schools.

But Stahl suggested charter schools can also hurt traditional public schools by taking away their resources. “Your argument that if you take funds away, that the schools will get better, is not working in Michigan,” she told DeVos.

Stahl mentioned Michigan schools' poor performance, something a University of Michigan study appeared to confirm last year.

Using National Assessment of Education Progress (NAEP) scores, University of Michigan professor Brian A. Jacob found that his state's students continually made the least improvement compared to those in other states since 2003.

But studies have shown mixed results in Michigan, DeVos' home state.

A 2003 study showed that with charter school competition, Michigan's public schools increased their productivity and achievement and improved their performance relative to schools not subject to competition. A 2005 study, however, found Michigan charter schools delivered no significant impact on their neighboring public schools' test scores.

What Does the Evidence Say?

The “60 Minutes” interview offered a glimpse into the confusion surrounding whether charter schools prompt improvements in public school performance.

Multiple literature reviews — which examine the field of existing evidence — have indicated that the studies conflict on whether charter schools' presence benefits traditional public schools' performance.

“In short, there's an empirical disagreement about whether charter schools will have positive or negative indirect effects on students in district public schools,” Brian P. Gill, a scholar at Mathematica Policy Research, wrote in November 2016.

Gill and his colleague, Kevin Booker, examined 11 studies, dating from 2004 to 2016, looking at the impact of charter schools on nearby public schools.

They found that the literature provided some support for the argument that charter schools improve public school performance and “almost none” for the opposite hypothesis. While six studies found positive effects, only one showed charter schools having a negative impact on public school performance.

Four of the studies, including one that looked at six major cities in the United States, found charter schools had no impact.

The Maine Education Policy Research Institute, an organization funded by Maine's state legislature and the University of Southern Maine, similarly found “mixed” results after reviewing the evidence.

The authors cited multiple studies showing public school improvement in Michigan and Florida — the two states considered by DeVos and Stahl — but many others that showed no improvement at all.

They also noted an Ohio study showing a “consistently small but significant negative effect” on performance in traditional public schools.

In conclusion, the authors backed the findings from a 2008 study that said that “results from available empirical studies are mixed and do not yet allow for firm conclusions about the effects of competition on traditional schools and non‐choosing students.”

When the Education Department reported on the issue in 2010, it similarly said that “no consensus has been reached on whether competition from charter schools has a positive impact on the academic achievement of students remaining in traditional public schools.”

Despite years of study on the topic, experts appear to be conflicted over whether charter schools improve public school academic outcomes. Due to the uncertainty, public debate could continue as DeVos' Education Department continues its pro-school choice agenda to the dismay of opponents like the NEA.