Far more American high school students are graduating compared to a decade ago. Those students are completing more courses, particularly rigorous ones. And their grades are higher, too.

But these heartening pre-pandemic trends, detailed in a new federal study, come with a significant asterisk. Those same high school students scored no better, and in some cases scored worse, than graduates a decade ago on national exams.

“The study shows a variety of positive developments,” said National Center for Education Statistics Commissioner Peggy Carr. “However, these improvements have not aligned with higher achievement.”

The new analysis, released Wednesday by an arm of the U.S. Department of Education, tracks transcripts of a representative sample of high school graduates in 1990, 2000, 2009, and 2019. The trends it finds are at once striking and puzzling, suggesting that teachers are adopting more lenient grading policies or that students’ improved skills aren’t being well measured by standardized tests.

The researchers show that recent graduates earned more course credits, particularly in core academic subjects. On average, students finished high school with 28 credits in 2019, compared to 27 in 2009 and 24 in 1990.

Students are also taking a more advanced set of classes. More students took courses in algebra, precalculus, geometry, chemistry, and physics in 2019 than prior years. (There was a small dip in the share of graduates taking calculus in 2019 compared to 2009.)

Overall, there has been a continuous decline in students finishing high school without earning at least four credits in English and at least three in math, science, and social studies.

Even as students have taken higher-level courses, their GPAs have steadily risen — from an average of 2.68 in 1990 to 2.94 in 2000, 3.0 in 2009, and 3.11 in 2019.

Students of all backgrounds have earned higher grades, although disparities have not changed much in three decades. On average, white and Asian students have higher GPAs than Black and Hispanic students. Girls, overall, have higher GPAs than boys.

On national exams taken at the end of high school, meanwhile, math and reading scores in 2019 were slightly lower than in 2009 and unchanged from 2005. Science scores haven’t budged since 2009.

Those disappointing results may in part reflect declining dropout rates, since more students are sitting for the exams than in previous years. But that doesn’t explain the coinciding rise in grades.

“The reasons for the apparent contradiction of increasing GPAs and coursetaking with falling NAEP scores are neither obvious nor simple,” as one Department of Education document puts it.

Grade inflation is one obvious explanation. Rising GPAs are not new, and have prompted decades of commentators to wring their hands at purportedly declining standards in American high schools. Pressure from parents, students, and policymakers — all wanting more students to graduate high school and enroll in college — may have led teachers to loosen grading policies.

Many fear that such inflation has harmful consequences.

“Grade inflation clouds measures of students’ true knowledge and skills,” wrote American University professor Seth Gershenson. “This means grades may mislead students, parents, and subsequent educators — not to mention potential employers and policymakers — about how children and schools are performing.”

Other experts say inflation is not inherently bad. “Higher grades could mean less discouragement from challenging subjects and maybe even greater confidence and persistence to graduation,” wrote Harvard education researcher Zachary Bleemer.

Regardless, lower standards are not the only possible explanation for the disconnect in the new data.

High school grades also measure skills that aren’t captured by standardized tests, including work habits and engagement in school, researchers have found. That leads to a more optimistic explanation — higher grades reflect real improvement that just isn’t being measured.

“If you’re in an algebra course, some of your grade reflects how well you’ve learned algebra, but it also reflects, did you participate? Did you turn your assignments in on time? Did you show up to class? Did you participate in class discussions?” said Matt Chingos, a researcher at the Urban Institute.

Those other factors likely reflect why grades have proved better predictors of success in college than tests, said Chingos. “The kind of stuff that’s associated with grades — showing up every day, keeping at it, persevering — is the kind of stuff that helps you graduate college,” he said.

Matt Barnum is a national reporter covering education policy, politics, and research. Contact him at [email protected]. Chalkbeat is a nonprofit news site covering educational change in public schools.