Across the nation’s schools, chronic absenteeism is up and student test scores are down, but how much is the former responsible for the latter?

Research from before the pandemic consistently showed that absences worsened student outcomes in both the short and long term. For instance, one study led by Jing Liu found not only that each absence lowered test scores and course grades in English and math but also that absences in ninth grade made students less likely to graduate on time and attend college.

But a lot has changed since the COVID-19 pandemic. Yes, students are now much more likely to be absent, but there is also some reason to think that absences might harm academic performance less than they once did. For instance, by posting learning materials online, giving more asynchronous assignments, and allowing multiple retakes of assignments, schools have arguably made it easier for students to pass courses and graduate without attending class.

Which students are absent has also changed. Students who once had good attendance are now missing more days of school and more likely to be chronically absent, but these students—who tend to be high-achievers—may do fine academically whether or not they show up for class. For both these reasons, we might expect absences to matter less than they once did.

Nonetheless, several recent studies show that absenteeism after the pandemic still matters a good deal. Exactly how much, though, is an open question.

In a recent paper from AEI’s Chronic Absenteeism Research Working Group, David Blazar and colleagues found that in Maryland and North Carolina absences affected achievement both before and after the pandemic, and more for math than reading scores.  After the pandemic, they found that impact was a bit smaller, by about 10 percent. Another earlier study led by Tom Swiderski found similar results in North Carolina, one of the states Blazar and colleagues studied. Meanwhile, Mariana Barragan Torres looked at Illinois and again found absences impact achievement on both sides of the pandemic, and again more in math than reading, but she also found the effect of absences post-pandemic actually increased—anywhere from 10 to 20 percent more in most grades.

Using different data and methods, these studies ultimately tell a similar story. At best, each absence matters a little less today, but with students missing so much more school now, the overall effect of absences on achievement is much bigger. At worst, each absence may matter more now, and there are far more absences.

To wit, depending on the estimate and measure of absenteeism you choose, reducing absenteeism to pre-pandemic levels could reverse somewhere between 8 percent and 19 percent of pandemic learning loss, with bigger gains for disadvantaged students and schools.

In short, the attendance crisis has dealt, and is continuing to deal, a serious setback to student achievement. Getting students back in school won’t by itself reverse the precipitous decline in American students’ test scores. But reversing the trend without improving attendance will be far harder.