# Casley Gera, 2024).

Finally, although the evidence primarily assesses the impact of class size on test scores, student repetition and promotion rates – which are generally closely linked to learning – may also respond to reductions in class size. Walter (2018), assessing evidence from a panel of 20 high-, middle- and low-income countries, estimates that reducing PTRs by improving the allocation of existing teachers between schools could improve student promotion rates by between 0.1 and 4.2 percentage points.

In this paper, we present evidence of the impact of a five-year package of interconnected interventions intended to reduce class size in eight disadvantaged districts of Malawi. The intervention, implemented over five years, constructed classrooms; provided additional finance to schools to support hiring of contract teachers and construction of learning shelters; and provided results-based finance to reward improvements in staffing in lower grades. The interventions were targeted to eight districts with longstanding disadvantages in staffing, learning environments, and learning outcomes, particularly for girls.

Employing administrative data and data from a nationally representative independent sample of public primary schools, we estimate the impacts of the intervention on class sizes, repetition rates, and test scores. We exploit the targeting of the interventions to particular districts to conduct differencein-difference analysis between schools and students in the targeted districts and those in a comparison group of 17 rural districts (all non-urban, mainland districts which did not receive a similar intervention). We find that the interventions succeeded in reducing PTRs and pupil-classroom ratios (PCRs) in lower primary; reduced repetition rates in lower primary by 0.7 points; and closed the gap in learning outcomes between the targeted districts and the rest of Malawi. We also find suggestive evidence that the treatment reduced the gap in learning between girls and boys. The findings suggest that even in a low-income environment with significant constraints, targeted efforts to reduce class sizes can close district-level gaps in learning.

Our study is one of the first to assess the impact of an interconnected set of interventions to reduce class sizes conducted at large scale. Previous experimental evaluations of interventions to reduce class sizes, such as those as described above, have been conducted on a small scale under pilot conditions.<sup>3</sup> While randomized evaluations have historically been considered the ‘gold standard’ for causal estimation of the impact of an intervention on selected outcomes (Cartwright, 2011), there is increasing concern that small-scale experiments can have low levels of external validity. Experiments in which allocation to treatment and control is done randomly, but from a purposively selected overall evaluation sample, may meet the technical definition of a randomized control trial without achieving representativeness of the target population (Deaton and Cartwright, 2018). Furthermore, even RCTs in which both sample selection and allocation to treatment are randomized, typically involve

> 3 For example, Duflo et al. (2015) employs a sample of 70 schools while Muralidharan and Sundararaman (2013) employs a sample of 100 schools.

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