Last week’s release of 2023 scores from the Trends in Mathematics and Science Study (TIMSS)—an international assessment measuring fourth and eighth graders in math and science—offers a fresh look at the academic performance of US and international students. The results are grim.

Three things stand out. First (and perhaps not surprisingly), the pandemic harmed student achievement. Between 2019 and 2023, US math scores cratered, dropping by 18 points for fourth graders and a whopping 27 points for eighth graders—huge declines on a scale where 30 points roughly equates to a year of learning. In science, declines weren’t statistically significant but were in the same direction.

Second, the lowest performing students were hit hardest. Looking beneath the averages reveals how students across percentiles fared in both grades and subjects, and the patterns—though not all statistically significant—are consistent and compelling. In fourth-grade math, the scores of students below the 50th percentile dropped precipitously while the 75th and 90th percentile hardly moved at all. This divergence is even clearer in fourth-grade science scores (click on the grade and subject selector) where the 10th percentile declined by 22 points while the 90th percentile went up by four. In eighth grade, scores fell similarly across percentiles in both subjects during the pandemic.

Because TIMSS scores vary so dramatically between percentile groups, the size of these changes can be hard to appreciate on a normal graph like the one above. So, to make the size of these changes clearer, I graphed percentile groups’ scores relative to their scores in 2011 (see chart below).

This second graph demonstrates the third thing that stands out in the TIMSS scores: Test scores for many groups—and especially for lower-performers—were already declining before the pandemic, reaching their high point in 2011 or 2015 and falling since.

We can see from this graph that the absolute achievement gap was widening well before the pandemic but that in certain cases the pandemic made the achievement gap even worse. Since 2011, the score gap between the 75th and 25th percentiles in fourth-grade math grew by 35 points—over a year’s worth of progress in learning for the average student. Similarly, the gap between the 90th and 10th percentiles grew by 58 points—about two years of learning—during that same period. 

In fourth-grade science, scores held up for all groups in 2015, and for the top half of scores through 2023. Meanwhile, for those in the 25th and 10th percentiles, scores dropped by over half a year’s worth of learning and achievement gaps grew by well over a year’s worth of learning.

In both subjects in eighth grade, the achievement gap did not grow during the pandemic. There is no comfort to be found here, however, because the downward pandemic trends are evident across the board.  Even with a constant gap during the pandemic, the gap grew dramatically in each subject since 2011.

It’s important to point out that not all these estimates are statistically significant. However, given how we have seen the same patterns in last year’s PISA scores, and NAEP scores before that, I have no doubt these trends are real, and dire. The floor is falling out on US student performance. Of course, TIMSS is an international test, which raises the question: What happened in other countries? More on that tomorrow.