The numbers appeared troubling.

During the 2016-2017 school year, 64 percent of English-language learners who took state reading exams in Virginia passed, according to state data. Two years later, passing rates plunged to 35 percent.

The precipitous decline was clear across all subjects that English-language learners were tested on — passing rates tumbled by 20 percentage points or more on Standards of Learning tests in reading, writing, science and history. Math scores for English-language learners dropped, too, although not quite as dramatically as in other subjects: In the 2018-2019 academic year, 59 percent passed state math exams, compared with 68 percent in 2016-2017.

But the numbers didn’t paint a complete picture.

The Virginia Department of Education had changed the way it calculated passing rates for English-language learners after an overhaul of federal education law, resulting in what appeared to be a significant drop-off in performance.

School systems monitor the progress of English-language learners after they gain English proficiency. Previously, Virginia education officials included the scores of those former English-language learners in their calculation of overall passing rates, for up to two years after the student was no longer classified as an English-language learner. That had the effect of inflating the passing rate for that group of students overall.

That changed with the most recent round of exams.

This time, the state did not include the scores of former English-language learners, which meant the results released in August reflected only the passing rates of students currently classified as English learners.

The state also recalculated passing rates for the 2017-2018 school year to remove the scores of students who had gained English proficiency, said Charles Pyle, spokesman for the Virginia Department of Education.

The state said it adjusted its calculations to comply with reporting requirements under the Every Student Succeeds Act, the federal education law that replaced No Child Left Behind, a test-based accountability system that became widely viewed as overly punitive and unrealistic.

In the future, Pyle said, the state plans on publishing data that show passing rates with and without the scores of former English-language learners.

“There is value in reporting a figure that does speak to the success of schools moving students to English proficiency, and so we’re looking at, eventually, reporting both pass rates in our public reporting,” Pyle said.

Sloan Presidio, an assistant superintendent in Fairfax County Public Schools, said students who are still learning English cannot be expected to perform as well on high-stakes standardized tests as their peers who are fluent in the language. Fairfax, the largest school system in Virginia, educates more than one-third of the state’s English-language learners.

“Students who are still learning to read and write English are at a significant disadvantage when trying to demonstrate their content knowledge on standardized tests that are written in a language in which they are not yet proficient,” Presidio said.

After English-language learners are given time to develop their reading, writing and speaking skills, they perform “at or above the division averages,” he said.

The Virginia Department of Education released state standardized test scores for the 2018-2019 school year on Aug. 13. Students begin taking Standards of Learning tests in third grade and sit for them through high school.

State officials have promised to work with school systems to burnish students’ reading skills, after the results revealed persistent and, in some cases, deepening gaps in scores between black and Hispanic students and their white and Asian peers.