For the vast majority of Indiana schools, test scores are the single largest factor determining state ratings, a source of frustration for some educators. But for 15 charter high schools that serve adults, test scores play a fairly minor role in how schools are measured.

Adult high school leaders say the grading model, which relies mostly on graduation data and students earning college credits or workplace certifications, is more accurate and relevant based on their unique student population.

While it’s the only alternative method for holding Indiana schools accountable outside of the traditional grading system, adult high school grades have garnered little public attention. State board members swiftly approved the 2018 grades without any comments or discussion earlier this month. But the method could be seen as a model for institutions asking to be evaluated in a different way, including virtual charter schools, a growing sector that has faced scrutiny for poor student performance.

In fact, educators and advocates pushing for alternative accountability models are already connecting the dots. At a meeting of the state’s virtual charter school committee last month, Veronica Brooks, policy director for the National Association of Charter School Authorizers, pointed to adult high schools as a model for how Indiana could alter regulations around online schools.

The stakes for schools are high — if an Indiana school gets four F grades in a row, the state board of education has to get involved, which could lead to takeover or closure.

The adult high school grading model was created in 2015 with the input of adult high schools across the state and the Indiana Charter Board, which oversees the Excel Centers. That happened at the same time that Indiana was also rewriting its grading model for other schools, a model that debuted in 2016.

Adult high schools enroll at least 50 percent of students who are age 18 or older and are coming back to school later in life, possibly after dropping out, or juggling other family and work-related responsibilities.

Of Indiana’s 15 adult high schools, the two Christel House dropout recovery schools received C’s, Gary Middle College received a B, and the 12 Excel Center schools received six As’ and six B’s. The Indiana State Board of Education approved the release of the grades at its meeting last week.

“Overall, we’re pretty satisfied with the way it reads,” said Kevin Teasley, founder of Gary Middle College, which enrolls adults and younger students and earned a B rating. “At the end of the day, it really is about students graduating and also getting college and career readiness.”

The grades are primarily based on a slightly complicated calculation that includes information about school enrollment, how many students graduate, and what advanced courses, college credits, or industry certifications a student has completed.

The schools can be dinged if too many graduates don’t pass the state’s required graduation exam (currently the 10th-grade ISTEP test), but it isn’t weighted significantly enough to bring a school from an A to an F.

For example, if no graduating students pass the test, a school could still earn a D grade if its students did well obtaining college credits or workplace certifications. Like grades for K-12 schools, the overall calculation results in a numerical score on a 100-point scale that corresponds with an A-F letter grade.

Adult high schools still have to give students the 10th grade ISTEP exam, and passing rates across the board are low — at Gary Middle College, for example, no students passed both English and math exams in 2018. At the Excel Centers, passing rates were below the state average (about one-third of students passing) or too few students took the test for results to be publicly reported.

Find your school’s 2018 ISTEP scores

Chris Domaleski, associate director for the New Hampshire-based National Center for the Improvement of Educational Assessment, said by focusing on outcomes — or what factors could indicate students are ready for life after high school — Indiana’s adult high school grading model appears to make sense for the kind of school it’s designed to measure.

“I think putting a heavy emphasis on those (outcomes) is probably a very good decision for the state,” Domaleski said. “It’s not helping alternative schools if the message given to them every year is, you failed. That doesn’t provide any useful information.”

Domaleski, who describes himself as a strong proponent of alternative accountability systems, says the models are best when they are created to fit the school in question — not when state officials just lower the standards of the traditional rating system and call it “alternative.” And states must still ensure, even if an alternate model is used, that those schools’ students who might be struggling and those from certain racial, ethnic, or other groups with intense needs, don’t fly under the radar.

Read: Indiana should do more to hold schools accountable for serving vulnerable students, analysis says

As the state transitions to new graduation rules that no longer require students to just pass the state exam to graduate, it’s not clear how this grading model could change, and the transition will likely affect both adult high schools and traditional schools. The state is also in the process of changing school letter grades, which has resulted in a fractured system that must incorporate ratings from the state and the federal government. It’s unclear there, too, how adult high school ratings could be changed.

Read: Indiana schools getting 2 state grades? Too confusing for parents and educators, experts say.

All schools can appeal their grades and sometimes receive no grade at all. Schools that tend to serve large numbers of students with severe cognitive disabilities, for example, have received “null” grades from the state. New schools and small schools can also use slightly different grading formulas, but they’re still within the typical model, and generally still rely on test scores.