High school students are earning more As, but average standardized test scores are falling.

A new study that examined graduates between 1998 and 2016 found the proportion of students with A averages increased almost 10 percent in under 20 years, climbing from 38.9 percent in 1998 to 47 percent in 2016. That means nearly half of all high school graduates earned an A average. The average grade point average also rose from 3.27 to 3.38 in the same time period.

Good news, right?

Consider also that, as the report documents, graduates' average SAT scores fell from 1,026 to 1,002 over that same 18-year stretch.

That means, in short, grades rose while standardized test scores dropped.

The study, released on Monday, was authored by Michael Hurwitz, a senior director at the College Board, and University of Georgia doctoral student Jason Lee. Given that the College Board administers the SAT, it's in their interest to promote the importance of standardized testing. But the pattern outlined in the study is strong enough to stand on its own.

Why would average GPAs rise so much at the same time average SAT scores are steadily declining?

Lee explained that the high schools "most prone" to this grade inflation "are the resourced schools … the ones with the highest level of affluence." As USA Today paraphrased, "the upward creep is most pronounced in schools with large numbers of white, wealthy students. And its especially noticeable in private schools, where the rate of inflation was about three times higher than in public schools."

Parents whose children are in districts with higher grade inflation may want to ensure their students' good report cards are adequately measuring their academic progress.

Emily Jashinsky is a commentary writer for the Washington Examiner.