Big Class, Small Gains? Reading, Classroom Quality, and the Moderating Role of Class Size in Northern Nigeria

• In Event: From Constraints to Change: Data-Driven Approaches to Transform Early Literacy

Proposal

Reducing educational disparities is essential to strengthening social cohesion, yet many pupils in low- and middle-income countries leave the early grades without acquiring basic reading fluency. Structured pedagogy programs—now central to the global quality agenda—deliver consistent gains, but the magnitude is too modest to bring most children to functional literacy (Evans & Popova, 2016; Gove et al., 2017; Piper & Dubeck, 2024). A key challenge is that reforms to improve instructional quality remain agnostic to structural constraints, especially overcrowded classrooms, that blunt their impact. While programs equip teachers with pragmatic coping strategies (such as grouping pupils, relying on choral responses, or establishing classroom routines), these adaptations are rarely sufficient where class sizes are extreme, and few reforms have the mandate or resources to confront such structural barriers directly.

Existing research—echoed in prevailing practice—appears to justify the current emphasis on pedagogy: economics literature commonly concludes that class size reductions are inefficient relative to other inputs (Glewwe et al., 2011). However, much of this evidence defines “large” as 40 or 50 pupils per classroom, levels that, while sizable, differ markedly from conditions in many low-resource settings. In Northwest Nigeria, the context for this study, public primary school classes average more than 50 pupils (UNICEF, 2021); in our sample, the average was even higher (65 to 71 pupils) with nearly one-quarter of classrooms enrolling over 100 students. In such environments, even high-quality practices face steep implementation barriers.

These conditions underscore the need to examine not only whether pedagogy matters, but also under what structural conditions its effects are realized. Research into instructional quality has typically treated structural constraints—such as class size and resource density—as background conditions or control variables, rather than as factors that may fundamentally mediate the effectiveness of pedagogical reforms. This presentation directly addresses that gap, demonstrating how structural conditions substantively reshape the returns to quality interventions.

Drawing on longitudinal data from 2,700 Grade 2 students and 600 teachers across Jigawa, Kaduna, and Kano states, we construct a composite measure of pedagogical quality that spans four domains: teacher guides, a scaffolded teaching approach, classroom management, and pupil textbooks and materials. We link these measures with student performance on the Hausa Early Grade Reading Assessment (EGRA) using regression models with student-, teacher-, and school-level controls, confirming that pedagogical quality is associated with literacy outcomes. We find that higher classroom quality significantly improves early reading outcomes: students in high-quality classrooms gain 0.34 standard deviations more than peers in low-quality classrooms.

However, these benefits are highly uneven. In smaller classes (≤40 pupils), high-quality instruction is associated with nearly one full standard deviation improvement in reading scores, while in larger classes the advantage shrinks to just 0.14 SD. Among the quality components, access to textbooks and teacher guides exhibit the strongest associations, but again only in classrooms below the overcrowding threshold.

While it may seem self-evident that large classes pose challenges, few empirical studies quantify how they reshape the effectiveness of quality reforms in low-resource systems. We do so directly. By using longitudinal data and a composite measure of pedagogical quality, we isolate the interaction between class size and instruction, showing where and to what extent reform gains erode. This moves the field beyond platitudes that “large classes are a problem” to rigorous evidence of their measurable impact on the cost-effectiveness of reforms. The study offers new and policy-critical evidence on how structural constraints mediate the returns to pedagogy, with direct implications for governments and donors seeking to balance investments in teaching quality against system capacity. More broadly, it highlights a critical tension: by treating “quality” as the singular solution to low learning, global discourse risks obscuring structural barriers that blunt reform impact and perpetuate inequality.

Authors

• Wael Moussa, FHI 360

• Rachel M Hatch, FHI360

• Caitlin Kim