could provide approximately 29 and 25 lumens of light, respectively. In comparison with traditional lighting devices used in Bangladesh, the kerosene-based open-wick lamp and the covered-wick lamp (“Hurricane” lantern) produce, on average, approximately 7.8 and 45 lumens of light, respectively (Mills and Jacobson, 2008).<sup>2</sup>

# **Sampling procedures**

We selected children who were attending primary and secondary schools as our target population for this study. More precisely, as very few variations in schooling performance or study hours were expected at the elementary level, we focused on children who were enrolled in the 4<sup>_th_</sup> to 5<sup>_th_</sup> grades of primary school and 6<sup>_th_</sup> to 8<sup>_th_</sup> grades of junior high school.

To select children (and their households) to participate in this study, we began by listing all of the primary and secondary schools located in the _Chars_ of the Gaibandha and Kurigram districts of northern Bangladesh; we then conducted quick initial inspections of the teachers and School Management Committees of these schools. To obtain internally valid estimates, without contamination effects, among all 28 schools in the eight _Chars_ listed, we restricted our sample to 17 schools in two _Chars_ , where SHS services provided limited coverage. Out of 1,665 total students belonging to the 4<sup>_th_</sup> to 8<sup>_th_</sup> grades in 17 schools, we initially selected 1,292 children as potential candidates for this study. The remaining 373 students were excluded, either because their homes (including school dormitories) had already been electrified, or because a sibling was one of the 1,292 students already chosen (i.e., for each household, we included only one child in our study sample). Potential participants were also excluded if their school attendance rate was lower than 80% over the previous four months. After drawing up an initial list of 1,292 students, we interviewed each child at his or her home to make sure that none of our participants had access to electricity or solar lights. Of these 1,292 children, we found 911 who had no access to electricity or solar lights at home during the period of our survey.<sup>3</sup> Of those, 882 became effective sample households for this study; the rest of the children in the sample had dropped out of school to get married or for other practical reasons (e.g., land erosion, resulting in forced migration) before the detailed baseline household survey was conducted. Figure S.2 in the supplemental appendix illustrates the detailed timeline for our surveys and interventions, along with Table S.1, which reports on the number of students selected through the screening process described above.

During the baseline survey conducted in July and August of 2013, we collected detailed data at the household level to understand the socio-economic conditions of the sample children and their households. The data included household demographic characteristics, details of energy use and its sources, expenditure, various income generating

> 2This does not necessarily mean that the traditional Hurricane lantern provides more brightness than the S2 and S10, because the former cannot maintain effective brightness/lumen for long hours due to the emission of carbon smoke.

> 3It emerged that the remaining students had access to SHS services, through the support of NGOs.

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