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After listening to nearly two hours of public comment in a statehouse hearing room, GOP Sen. Chris Garten’s support for more funding for charter schools came down to one big thing: academic outcomes.

The Feb. 11 hearing was part of a debate over a controversial bill — now passed by lawmakers — that would require Indianapolis Public Schools to share property tax revenue with charters.

“In charter schools in Indianapolis, there’s 64 days [of] additional learning in reading,” Garten said, citing a 2022 Stanford University study that also found charter students gained over 100 additional days of learning in math. “These students are accelerating at a faster rate. That’s what we should care about.”

The Stanford study is one of several that Republican lawmakers and pro-charter groups have used in recent years to argue that charters have an academic edge over traditional public schools. They’ve come up not only in public hearings, but in blog posts, media coverage, and elsewhere.

To some politicians and charter advocates, the studies clearly answer the one question underpinning the funding debate: Which system performs better, charter schools or IPS?

But the answer may not be so simple.

Some academics have voiced concern with the methodology of some of these studies, and that they should not be used to make broad conclusions about different types of schools.

Meanwhile, results from state standardized tests and national exams do favor charter students in certain instances, although not necessarily overall.

Disputes about the relative merits of charters and traditional public schools have become common in urban school districts. Still, pitting one school type against another is ultimately not the right approach, said Jon Valant, director of the Brown Center on Education Policy at the Brookings Institution. When charter schools open in a community, he said, it’s more important to measure how and whether students across all sectors improve.

“I think we sometimes miss the big picture,” Valant said. “And we really should be focused on: How is the presence of charter schools affecting students overall?”

Here’s a breakdown of studies and test scores often cited in the ongoing conversation about charter schools and IPS — and what to keep in mind about the data.

Do charter students get more ‘days of learning’?

The study cited by Garten is the Center for Research on Education Outcomes at Stanford University’s 2022 Indianapolis study, which examined state standardized test results from 2017-18 and 2018-19. The study looked at students in independent charters, schools in the district’s autonomous Innovation Network (many of which are charters), and IPS.

The study from the center, also known as CREDO, then compared those students to statewide average learning gains, and converted the difference into a nominally straightforward metric: days of learning.

CREDO’s study found that charter students on average acquired more days of learning in reading and math than those in district schools.

Among the significant differences between the school sectors measured in 2018-19 are:

  • Students in charter schools demonstrated greater growth in math than those in district schools.
  • Black students in charter schools demonstrated greater growth in reading and math than Black students in district schools.
  • Hispanic students in charter schools demonstrated greater growth in reading and math than Hispanic students in district schools.
  • Charter school students in poverty demonstrated greater growth in reading and math than district students in poverty.
  • Special education students in charter schools demonstrated greater growth in reading than special education students in district schools.

CREDO has published high-profile studies of charters for over 15 years. A 2023 study it produced of charter schools nationwide determined that charters outperform district schools in both reading and math.

But some of CREDO’s methodologies have drawn criticism from other researchers.

One of their concerns: Translating data into 97 extra days of learning for charter school students, as one metric in the study concludes, may overplay the actual difference in results.

“You’re having to make these assumptions about the number of days of learning happening throughout the year,” said Joseph Ferrare, an associate professor at the University of Washington Bothell who has studied charter school authorizing in Indianapolis. “That’s why I think for the most part the research community hasn’t reached any consensus on using that as a method.”

A number of the report’s findings about charter schools and district schools — such as the gap of 64 days of learning Garten referenced at the hearing — are tied to numerical differences that are not statistically significant, Ferrare said. In other words, there is not enough evidence to rule out the possibility that the performance of the two types of schools is actually the same, according to Ferrare.

Some findings are not statistically significant because charter schools have a lot of variation in their performance, said CREDO director Margaret Raymond.

She also noted the 2022 Indianapolis study’s data is becoming outdated.

But Raymond advised against drawing conclusions from the study about whether district schools or charters perform better. Instead, she noted that the study found growth at charter and Innovation schools equivalent to the state average. District schools, meanwhile, showed growth below the state average.

“The point is that somehow, the rules of the game for charter schools and innovation schools allow them to actually be better,” she said. “And what are the conditions of those? What is it about those rules of the game that give them that kind of capacity to perform at higher levels?”

Indianapolis charter schools more cost effective, study finds

Another 2023 analysis from the University of Arkansas’ Department of Education Reform concluded that Indianapolis charter schools produce better academic outcomes on fewer dollars.

Using data from CREDO’s Indianapolis study, the analysis converted differences in test scores into scores on the nationwide National Assessment of Educational Progress. It then analyzes those scores using per-pupil revenue data for the 2019-20 school year.

The report concludes that Indianapolis charter schools are more cost-effective and earned an additional 11 NAEP points per every $1,000 in funding, compared with traditional public schools.

But Ferrare cautioned that the report makes too many assumptions and does not control for factors that would drive differences in spending between schools, such as students with a particular set of needs, Ferrare said.

While charters have a higher percentage of Black students and those eligible for free or reduced-price meals, IPS has a higher percentage of students with disabilities and a slightly higher proportion of English language learner students, according to a Chalkbeat analysis of 2024-25 enrollment data.

But differences in student population do not track closely with differences in spending across the school types, with the exception of funding for students with disabilities, said Patrick Wolf, distinguished professor of education policy in the Department of Education Reform and one of the study’s co-authors.

Even then, the “yawning funding gap” between IPS and charters can’t ultimately be justified by student demographics, Wolf noted.

What ILEARN results show

As prominent as those two studies have been in the debate over Indianapolis schools, the data they use is several years old. So what do more recent student achievement results tell us?

The latest 2024 ILEARN results for students in grades 3-8 show that there is little overall difference between charter schools and IPS schools in English language arts and math.

That’s according to a Chalkbeat test score analysis, which includes all charters within IPS borders, as well as those outside of IPS borders where a majority of their students live in IPS borders.

When it comes to several student subgroups, charters have the edge.

Black charter school students achieved higher average proficiency rates than their peers in IPS-run schools in both reading and math. Charters also had higher average proficiency rates for English language learners and those qualifying for free or reduced-price meals in both subjects.

What IREAD, SAT results, and graduation rates show

On last year’s IREAD test for literacy given to third graders, charter schools had a weighted average passing rate of roughly 64%, compared with the district’s overall average of 60%.

On the SAT, Indianapolis-area charters show a higher average percentage of students scoring at least a 480 in reading and writing and a 530 in math on the SAT — scores that the College Board says demonstrate college readiness.

But experts still caution against using these stats to reach sweeping conclusions about entire school systems or sectors.

The test results alone don’t show whether the schools alone are causing them, Ferrare said, and there may be other characteristics of the student population accounting for the differences.

Meanwhile, graduation rates for non-waiver students — those who don’t receive an exemption from state graduation requirements — are slightly higher in IPS than in charters.

Is pitting charters against traditional public schools unhelpful?

One thing the Indianapolis education community doesn’t lack is a steady stream of research about its public schools.

A 2019 study from Indiana University researchers, for example, found that elementary students who were continuously enrolled in a mayor-sponsored Indianapolis charter school performed better on the state standardized test than students in traditional public schools.

And a 2023 study from Ferrare and others also found positive results for students who switched from a traditional public school to a charter school authorized by the mayor’s office.

At the same time, a 2025 paper examining the IPS “portfolio” model of different school types — which includes charters — found that the autonomy provided to portfolio schools did not significantly affect student achievement.

At the end of the day, Valant said, measuring which school type is better academically is complicated.

“I wish we could talk more about how these policies affect overall student outcomes and family outcomes,” he said, “because I think sometimes the horse race comparison can be distracting, and also can create some bad incentives and can kind of keep schools from wanting to collaborate.”

Amelia Pak-Harvey covers Indianapolis and Lawrence Township schools for Chalkbeat Indiana. Contact Amelia at apak-harvey@chalkbeat.org.