Though many factors influence the relationship between amount of instructional time and student achievement—primarily, the quality of the instruction and the students’ readiness to learn—instructional time remains a crucial component in considering students’ opportunity to learn. Instructional time was calculated using principals’ reports on the number of school days per year and the number of instructional hours per day and teachers’ reports on the weekly number of hours of mathematics instruction, as explained in Exhibit 12.1 (see About the Scale). Exhibits 12.2 and 12.3 present principals’ and teachers’ reports about the instructional hours per year overall spent on mathematics instruction in fourth grade and eighth grade, respectively. Countries are ordered by the number of hours per year for mathematics instruction.

On average, the fourth grade students across the TIMSS 2019 countries received 895 hours per year of instruction across all subjects, and 154 hours, or about 17 percent of the total, were devoted to mathematics instruction. The number of hours devoted to mathematics instruction ranged from a high of 250 hours in Portugal to 101 in Korea. The amount of mathematics instructional time relative to total instructional time varied considerably across countries, reflecting different approaches to organizing and addressing the mathematics curriculum. As might be anticipated, within-country estimates of instructional time can vary somewhat from the levels of instructional time established by policy (see *TIMSS 2019 Encyclopedia*).

The eighth grade students across the TIMSS 2019 countries received an average of 1,023 hours of instruction across all subjects, and 137 hours, or 13 percent of the total, were devoted to mathematics instruction. The number of hours for mathematics instruction ranged from 200 in Chile to 102 in Cyprus. Of the countries that participated in TIMSS at the fourth and eighth grades, in most countries, the number of annual hours devoted to mathematics instruction decreased between fourth and eighth grades, likely because by eighth grade, the school curriculum covers many more subjects than in fourth grade.

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