The clarity with which teachers convey the curriculum to students has significant implications for student learning. Students were asked about aspects of teachers’ instruction during their science lessons: whether they know what their teacher expects them to do, and whether their teacher is easy to understand, has clear answers to their questions, is good at explaining science, does a variety of things to help the students learn, links new lessons to previous knowledge (eighth grade only), and explains a topic again when the students do not understand. Responses were combined into the TIMSS 2019 Instructional Clarity in Science Lessons scale, as described in Exhibit 13.8 (see About the Scale). Exhibits 13.9 and 13.10 present students’ reports about the clarity of their science lessons, for fourth grade and eighth grade, respectively. Countries are reported by percentage of students reporting “high clarity of instruction.”

On average, slightly less than three-quarters (72%) of fourth grade students reported “high clarity” of instruction in their science lessons, 22 percent reported “moderate clarity,” and just 6 percent characterized their lessons as having “low clarity.” There was a range in views across countries with, interestingly, lower percentages of students characterizing their lessons as having “high clarity” in some of the higher performing countries, such as Korea and Japan. On average, internationally and within most countries, however, higher clarity was associated with higher average achievement. Across countries, average achievement was 498 among students reporting “high clarity” of instruction, 480 among students reporting “moderate clarity” of instruction, and 466 among students reporting “low clarity” of instruction.

Eighth grade students’ reports are presented separately for countries in which science is taught as an integrated subject in eighth grade (first panel of the exhibit) and for countries in which science is taught as separate subjects (following four panels). Eighth grade students were, on average, less positive about the clarity of their science instruction compared with fourth grade students. Similar percentages of students reported “high,” “moderate,” and “low clarity of instruction” for integrated science, biology, chemistry, physics, and Earth science. For all science subjects, 44 to 49 percent of eighth grade students, on average, characterized instruction as having “high clarity,” 38 to 41 percent reported “moderate clarity,” and 12 to 16 percent reported “low clarity.” As seen in fourth grade, clarity of instruction was positively associated with science achievement. In countries teaching science as an integrated subject and for each of the separate science subjects, average achievement increased with each successively higher level of students’ reports of instructional clarity.