# **1. Introduction**

A growing body of research shows that a child’s early life has consequences for later life outcomes in education (Bhutta et al., 2002; Brennan et al., 2012; Duncan et al., 2007; Feinstein and Duckworth, 2006; Melhuish et al., 2008; Moser et al., 2012), health (Hertzman, 2013), and social capital (Moffitt et al., 2011). Healthy child development is an enabler of human capability allowing children to reach physical maturity and participate productively in economic, social and civic life (Conti and Heckman, 2012; Sen, 1999). Many of the problems arising in early childhood have social and financial costs that cumulatively represent a considerable drain on a country’s resources (Feinstein and Duckworth, 2006; Victora et al., 2008).

High-quality preschool programs provide an opportunity to mitigate the risk factors that many young children face (Barnett, 2011; Duncan et al., 2007; Duncan and Magnuson, 2013; Heckman, 2006; Shonkoff and Phillips, 2000). Given the high-risk factors faced by children growing up in middle- and low-income countries (Engle et al., 2011), the effectiveness of preschool programs is likely to be large for these children. However, much of the evidence base on the long-term impacts of preschools has focused on three “iconic” projects in the United States: Perry Preschool, Abecedarian, and the Nurse Family Partnerships (Shonkoff, 2014). These studies examined high-intensity interventions in the United States that were run with small sample sizes in the late 1960s to early 1970s. While all have had longitudinal followups, few interventions have been implemented since that match either the fidelity or the intensity of these interventions.

In developing country settings, rigorous evaluations of preschool programs have emerged in the last decade. Results have ranged from no effect in some settings (Bouguen, Filmer, Macours and Naudeau, 2017) to positive effects in others (Brinkman et al., 2017; Jung and Hasan, 2016; Burger, 2010; Martinez, Naudeau and Pereira, 2012; Nores and Barnett, 2010). Systematic reviews of preschool interventions in developing countries reinforce the wide range of impacts seen in international settings (Tanner et al., 2015). The contrasting evidence from different settings has led some to question whether early childhood education can even have lasting impacts (Stevens and English, 2016).

In this paper, we contribute to the growing literature on the longer-term impacts of preschools in developing countries. We examine the longer-term impacts of early childhood education in a developing country setting using data on two cohorts of children from the Indonesia Early Childhood Education and Development (ECED) Project. The project lasted five years and expanded access to community-based preschools by providing block grants to villages to establish up to two playgroups (targeted for ages 3-4), providing teacher training, and raising community awareness about the importance of early education.<sup>1</sup> The _older cohort_ in our study was age 4 and the _younger cohort_ was age 1 when the project began.

The older and younger cohorts differed in terms of (1) the phase of project implementation when they were exposed to playgroups and (2) the length of exposure to playgroups at the appropriate age. On the first distinction, the older cohort was exposed to playgroups during the project’s first year since they were already age 4 at the start of the project. In contrast, the younger cohort was exposed to playgroups during the project’s third year when they turned 3 years old. As a result, the two cohorts experienced the same project at different phases of implementation. On the second distinction, the older cohort was at the upper-end of the appropriate age for playgroup attendance (age 3-4) when they were exposed to the project. In contrast, the younger cohort was only 1 year old when the project started, which meant that

> 1 In practice, at the start of the project, the playgroups allowed enrollment for children ages 3-6. See Brinkman et al, 2017a for further discussion.

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