Eighth-grade students’ reports are presented separately for countries where science is taught as an integrated subject in eighth grade (Exhibit 5.3.3a) and for countries in which science is taught as separate subjects (Exhibits 5.3.3b to 5.3.3e). In integrated science, about half of the students (51%) reported “high” instructional clarity, 35 percent reported “moderate” instructional clarity, and 14 percent reported “low” instructional clarity, on average. Generally, similar percentages of students reported “high,” “moderate,” and “low” instructional clarity for the separate science subjects of biology, chemistry, physics, and earth science. For these separate science subjects, 46 to 49 percent of eighth-grade students, on average, characterized instruction as having “high clarity,” 36 to 37 percent reported “moderate clarity,” and 14 to 18 percent reported “low clarity.” On average, internationally and within most countries, reporting greater instructional clarity was associated with higher average science achievement for eighth-grade students (Exhibit 5.3.3a to 5.3.3e). In integrated science, students who reported experiencing “high” instructional clarity had an average achievement of 496, students who reported experiencing “moderate” instructional clarity had an average achievement of 477, and students who reported experiencing “low” instructional clarity had an average achievement of 462. Average achievement differences follow the same general pattern but are less pronounced in the separate science subjects. Students who reported experiencing “high” instructional clarity had the highest average science achievement (ranging from 458 to 473 across subjects), but there were very small or no differences in average achievement between students who reported experiencing “moderate” or “low” instructional clarity (average achievement ranged from 448 to 456 and 448 to 453, respectively).