The study is the first in-depth analysis of student performance for the state's young charter school network, which was granted more stable legal footing by a state Supreme Court ruling in 2018.

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In a report released Tuesday, researchers from Stanford University took on a question that Washington’s state auditors could not:

What kind of academic impact do the state’s charter schools have on their students?

Their answer, after studying three school years’ worth of data: Overall, charter-school students’ scores on state math and reading exams grew at a similar pace compared to their peers enrolled in traditional public schools.

That finding was true for almost all student racial and demographic groups, with English learners being the notable exception. Students learning English who were enrolled in charter schools performed considerably better. Compared to English learners in traditional public schools, the report found they gained the equivalent of 83 more days of instruction in both reading and math. For that, the report had no explanation:

Nothing in the data that we crunch gives us any understanding of what is actually happening inside the schools,” said Macke Raymond, director of Stanford’s Center for Research on Education Outcomes (also known as CREDO), the group behind the report. 

Charter schools in Washington state are publicly funded, but privately run. Charter-school opponents in Washington and beyond claim the schools take money away from traditional public schools — as both receive funding from the state based on their enrollment — and aren’t directly accountable to voters because they are not controlled by elected school boards.

The study is the first in-depth analysis of student performance at the state’s young charter-school network, which gained more stable legal footing from a state Supreme Court ruling in late 2018.

The researchers also used a method called virtual control record, in which they analyzed and compared a little over 1,000 charter-school students with how their virtual academic and demographic “twin” in a traditional public school would have performed on state assessments.

The results of the comparisons are limited by a few factors, including the short history of charter schools here, and the demographics of charters schools, which generally enroll a larger share of nonwhite students.

Even so, Raymond says the measurements provide an important benchmark for comparing results — and measuring progress — in the future.

For example: The researchers found evidence that black students enrolled in charter schools saw similar growth in reading and math as white students in traditional public schools. (There was a small, but statistically insignificant gap in reading.)

By contrast, within traditional public schools, black students “exhibit 71 fewer days of learning in reading and 59 fewer days of learning in math” than their white peers, according to the study.

The results also showed variation between charter schools, with some significantly outperforming their local school options — by margins higher than the national average — and others falling behind.

Charter-school students in the Seattle area had the highest one-year gains in learning compared to their counterparts, beating out Tacoma and Spokane, two other hubs for charters in the state.