Effort on homework has a profound impact on student achievement. Researchers typically use an interindividual research design to explain homework effort. In this study with a total of 511 students from Grades 8 and 9, an interindividual perspective (focus on between-students differences) was combined with an intraindividual perspective (focus on within-student differences). Multilevel modeling showed that students' homework effort was a function of between-students differences in conscientiousness and within-student differences in perceived homework characteristics (subject-specific quality of tasks and homework control), perceived parental valuation of specific subjects, and homework motivation (subject-specific expectancy and value beliefs). Furthermore, a significant cross-level interaction indicated that perceived homework control by teachers had a stronger effect on students low in conscientiousness than on their more conscientious peers.