US scores on the 2023 Trends in Mathematics and Science Study (TIMSS) are another sign not only that American students are losing ground in math and science, but that the achievement gap between high-performers and low-performers has grown dramatically. As I wrote a couple days ago, these trends started well before the pandemic and are evident in TIMSS and several other nationally representative assessments.

What I want to look at today is whether these trends parallel what is happening in other countries. TIMSS is taken by hundreds of thousands of students across the world and can give us a sense of how US students compare to those in other nations both in absolute terms and in terms of achievement gap growth.

In absolute terms, the US is slipping in the TIMSS international rankings in both subjects, but more so in math. Those shifts are very real concerns, even if there are good reasons to treat international comparisons with some degree of caution.

On a more ignominious note, when it comes to achievement gap growth between 2011 and 2023, the US stands apart from its international peers—and not in a good way.

The charts below (toggle between different countries to compare) show the change in the test scores of different percentile groups since 2011—the TIMSS year nearest the apex of US achievement on multiple tests in multiple subjects. In these graphs, apparent differences are not all statistically significant, so take caution in reading too much into particulars. That said, the pattern of differences makes clear that the US has experienced uncommonly large and consistent achievement gap growth over the past twelve years.

This is not a worldwide problem, nor solely a pandemic problem. It is an uncommonly US problem.

For instance, in grade four math the gap between the 90th and 10th percentiles grew by more than 50 points. This means that the 10th percentile is nearly two years further behind the 90th percentile compared to where it was just 12 years ago.

This kind of achievement gap growth was similar but slightly smaller in eighth-grade math—48 points—but for both grade levels the US has larger achievement gap growth than any of the other countries shown during this period. 

The countries displayed are those with full data between 1995 and 2023, but even for the intrepid who want to peruse all countries with complete TIMSS scores since 2011, you won’t find another country with as much gap growth in either grade (see Grade Four Math and Grade Eight Math).

Of course, choosing 2011 as a reference point influences these comparisons, but the point here is not that US achievement gap growth is unprecedented in international contexts. Rather, the point is that there has been dramatic achievement gap growth over the past 12 years and that this achievement gap growth does not appear to be solely due to global factors beyond our control. This is an American problem, and it’s not just in math either.

In science, the US achievement gap growth was among the largest for countries with comparable data. In both grades four and eight the 90/10 gap grew roughly 40 points, well over a year of learning. In both grades, the US has larger gap growth than any of the countries shown in the charts below.

If you care to get deep into the weeds, you will still see that the US achievement gap growth in fourth-grade science since 2011 is truly exceptional. Indeed, it is larger than the achievement gap growth in fourth-grade science since 2011 (or in any timespan from 2011 on) for any other country with complete TIMSS scores since 2011. However, in eighth-grade science, between 2011 and 2023, of 25 countries, only the UAE, Hong Kong, and Sweden had larger achievement gap growth than the US did. (And England also did if you start in 2015 instead of 2011).

Again, it’s important to note that not all of these differences are statistically different from one another. However, they show the stark growth in US achievement gaps on TIMSS. From 2011 to 2023, US achievement gap growth estimates in fourth and eighth-grade math and in fourth-grade science were larger than those in every country with comparable data on TIMSS. And in eighth-grade science, the US gap estimates were larger than they were for all but a handful of countries. This sort of US educational exceptionalism is bad for our lowest performers and bad for the country.