that finds mixed results. While positive short-term effects on child development are reported for Mozambique (Martinez et al., 2017b), other studies find insignificant or even negative effects (Brinkman et al., 2017; Bouguen et al., 2018; Blimpo et al., 2019; Bernal et al., 2019).<sup>4</sup> Differences in socio-economic conditions, along with the nature and quality of a preschool program and its counterfactual (quality of other preschool arrangements or quality of parenting), make it difficult to draw broad conclusions that are applicable across contexts, particularly when these differences are unobservable or undocumented. Specifically, the literature often lacks detailed information on both the quality of the preschool supply and a clear understanding of the preschool demand mechanisms. Similar issues exist for the literature in higher income countries where large and long-lasting impacts (Belfield et al., 2006; Carneiro and Ginja, 2014) coexists with disappointing (Puma et al., 2012) and even negative results (Baker et al., 2008, 2019).

The presence of alternative programs may, in particular, explain some of the lack of consistency in the literature on preschool impacts. Most large-scale randomized controlled trials aimed at measuring preschool effects in low-income countries are implemented in an environment where (non-household-based) alternative care arrangements are present. For instance, in a previous preschool experiment conducted in Cambodia from 2008 to 2010, Bouguen et al. (2018) find that 11% of the control group attended a preschool. Similarly, 8% of a control group in Mozambique attended preschool (Martinez et al., 2017a), 16% did so in The Gambia (Blimpo and Pugatch, 2017), and 15% in Indonesia (Brinkman et al., 2017). In the US, 40% of families that lost a lottery to enroll in Head Start ultimately benefited from a close substitute program (Puma et al., 2012). The fact that all of these studies implicitly have different degrees of substitution, along with the fact that the quality of alternative childcare programs is often unknown, makes it impossible to draw general conclusions regarding the effectiveness of preschool interventions. We suspect that this lack of consistency in the literature is at least partially a result of variability in the type of specific substitution patterns we document in this study.

We contribute to the literature in four different dimensions. First, we provide evidence on a large, well-implemented public preschool construction program in rural Cambodia, with detailed information on both children and on the quality of the new preschool services provided. The key outcomes of interest are preschool and subsequent school enrollment, along with child cognitive and socio-emotional development. We collected three rounds of data on about 7000 children to analyze impacts.

Second, using T2 and T3 treatment branches, we analyze the effect of strategies to increase preschool demand and parental involvement. In particular, preschool

> 4Evidence on preschool programs in low- and middle-income countries based on non- and quasiexperimental study designs generally points to positive effects of preschool attendance (Berlinski et al., 2008, 2009; Engle et al., 2011; Rao et al., 2014).

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