<p>Motivational characteristics may shape how students perceive mathematics classroom instruction. Student ratings are widely used to assess instructional quality, but the specific roles of motivational student characteristics and prior achievement in shaping student ratings are not yet fully understood. Moreover, little is known about whether teachers adapt their instruction over time in response to motivational class characteristics. This study addresses (1) how student ratings of instructional quality relate to students’ motivation and prior achievement at the student and class level and (2) whether teachers adapt their instruction over time based on class-average motivation, class-average achievement, and within-class heterogeneity in these characteristics. Data from 1654 eighth-grade students across 73 classes were analyzed using multilevel modelling. Mathematics achievement and mathematics-related motivation (interest, self-concept, and intrinsic motivation) were assessed early in the school year. Instructional quality—encompassing classroom management, cognitive activation, and student support—was measured both early and late in the school year. Early in the school year, higher prior achievement and intrinsic motivation were associated with higher instructional quality ratings at both the student and class level. Additionally, at the student level, self-concept was positively linked to all three instructional quality dimensions, while interest was specifically associated with student support. Longitudinally, prior achievement and initial perceptions predicted later ratings. Moreover, higher heterogeneity in interest was associated with lower cognitive activation, and higher heterogeneity in intrinsic motivation with lower student support. The findings underscore the need to account for classroom composition—particularly in terms of student motivation—when examining student-reported instructional quality.</p>