Portable solar lights have attracted increasing attention as an alternative, affordable lighting source in hard-toreach areas (World Bank, 2010). It is expected that children who use them can gain additional study hours that could contribute to improving their academic performance (Esper et al., 2013). However, empirical studies aimed at systematically understanding the impact of solar lights are still scarce. This study intends to fill this knowledge gap by rigorously evaluating the impact of solar lanterns on a range of children’s educational performance, such as time usage, school attendance, and educational achievement.

The areas under study are the river islands of Bangladesh, known locally as _Chars_ . These river islands are prone to cyclical river erosion and floods, which frequently result in losses in terms of economic activities, possessions, and homes, thus disrupting families, livelihoods, and earnings. There is no provision of grid electricity in these river islands, and the Rural Electrification Board (REB) of Bangladesh has no plan to expand national grid-based electricity to _Chars_ due to their susceptibility. Moreover, while part of the population have access to a large solar photovoltaicpanel-based electricity system, known as Solar Home Systems (SHSs), portable solar products were not available in the study location during the time of this research. These local settings are ideal for our study, less likely to suffer from attenuation of the true solar impacts due to contamination.

Exploiting this region’s unique condition, we conducted an RCT in _Chars_ located in northern Bangladesh, where we provided solar lanterns to a randomly selected subset of the population for 16 months (September 2013 to December 2014). Our target population comprised 4<sup>_th_</sup> to 8<sup>_th_</sup> grade students in primary and junior high schools whose academic performance was more likely to be affected by the possibility of nighttime study than that of elementary grade children. We selected 882 sample children and households for our study, and implemented the within-grade randomization at each school. To differentiate the treatment intensity, a proportion of the students received a bundle of a main highcapacity solar device along with two smaller lanterns, another proportion of the students received only one main high-capacity solar device, and the remainder acted as a control group and received no devices. The ratio of each group is approximately 5:4:9, respectively. In our experiment, no students that were offered solar products refused to take the While a handful of recent empirical studies have explored the socio-economic impacts of solar products, our experiment displays a striking strength for three reasons. First, our study is the first relatively large-scale randomization to evaluate the impact of better nighttime lighting on education. For example, previous studies have typically been based on small-scale pilots, and hence suffered from low statistical power due to their limited sample sizes: 155 in Uganda (Furukawa, 2012, 2014), 341 in Kenya (Hassan and Lucchino, 2016), and 300 in Rwanda (Grimm et al., 2016). Second, in contrast to the previous research conducted in areas that already had an influx of portable solar products in local markets, our study was situated in a location that was free from potential contamination by portable solar 3