The TIMSS 2019 results reinforce the already extensive body of research showing a powerful positive relationship between students’ socioeconomic environment and their educational achievement. As shown in Exhibit 5.4, the eighth grade Home Educational Resources scale is based on students’ reports about the number of books and other study supports in their homes, as well as the highest level of their parents’ education (see About the Scale). As also explained, students were assigned a score on the scale according to the availability of these three home educational resources.

Exhibit 5.5 presents for each country the percentage of students in three categories of the scale, together with average student achievement in mathematics. Countries are ordered by the percentage of students in the “many resources” category, with an average percentage across countries of 14 percent. Educational resource availability varied widely across countries, with the percentage of students in the “many resources” category ranging from 2 percent in South Africa and Morocco to 40 percent in the Korea. The majority of students (73%, on average) were assigned to the “some resources” category, with 13 percent in the “few resources” category. There was a 113-point difference in the average mathematics achievement of students in the “many resources” category compared with the “few resources” category (546 vs. 433). Average mathematics achievement for the students in the “some resources” category was in between, at 488 points.

The second panel of Exhibit 5.5 presents a scatterplot showing the relationship between average Home Educational Resources and average mathematics achievement across countries. There is a modest positive association between Home Educational Resources and average mathematics achievement at the country level.

Exhibit 5.6 presents the same Home Educational Resources data, but this time in conjunction with average science achievement. The overall pattern of results is similar to mathematics, with an average science achievement gap of 118 score points between students in the “many resources” and “few resources” categories (549 vs. 431). Average science achievement for the students in the “some resources” category was again in between, at 489 points. Also similar to mathematics, the scatterplot in the second panel of Exhibit 5.6 shows a modest positive relationship between average Home Educational Resources scores and average science achievement across countries.