schools and with the distribution of schools across regions being in proportion to their relative population size (using the 2002 census). The final sample consists of 62 schools in Lindi, 138 in Morogoro and 220 in Shinyanga.<sup>15,16</sup> Schools were initially randomly assigned to different treatment groups using a three-step process. First, for each region, a natural category (region, district, or combination of districts) with about 60 schools was constructed.<sup>17</sup> Second, within each natural category, we generated a ranking of school quality using Form II pass rates (derived from Inspectorate Data) and then we created three strata using terciles of the pass rate ranking.<sup>18</sup> Third, random assignment was undertaken as follows: (i) within each tercile, half of the schools were randomly assigned to receive teacher incentives with other half as control; (ii) within the teacher incentives arm, half of the schools were randomly assigned to teacher incentives only and the other half to teacher incentive plus student incentives; and (iii) within the control arm, half of the schools were randomly assigned to receive another treatment which turned out to be unfeasible and these schools were not visited again in Phase 1, with the other half assigned to have continual data collection during phase 1. This produces a sample with phase 1 assignments of roughly 25 percent to teacher incentives only, 25 percent to both teacher and student incentives, 25 percent to unfollowed control, and 25 percent to followed control.

In phase 2, half of the schools in which teacher incentives had been implemented (either with or without student incentives) were randomly selected to continue with the scheme, and half of the schools were selected to discontinue it. In addition, the control group from phase 1 (including the unfollowed arm) was randomly split into a pure control group and a student-incentives only group. This produces a sample with phase 2 assignments of roughly 25 percent to teacher incentives (repeated), 25 percent to teacher incentives withdrawn, 25 percent to student incentives, and 25 percent to control.

> 15 At the time that the sample was generated, a list of replacement schools was also generated from the population of schools. Schools were replaced for two reasons: (i) the school was no longer functioning or where duplicates were found; or (ii) the school either did not have a Form 3 cohort or had 10 Form 3 students or fewer. 16 At the time of Phase 1 Baseline (November 2012), the full impact evaluation sample of 409 schools included 206 control schools. These 206 schools were then sub-divided into two groups - 105 pure control schools which were not visited again in Phase 1 and 101 control schools which were visited in Phase 1. Consequently, in Phase 1 midline and endline, the total number of schools visited is 304 (409 – 105). In Phase 2, the 105 pure control schools were added back to the evaluation sample.   Between Phase 1 Baseline and Phase 2 Baseline, the school attrition was around 13 schools (409-396), due to school closures or school desire not to participate further in the impact evaluation.  During Phase 2 another 3 schools dropped out of the evaluation. The school sample is smaller for Phase 2 midline (385) because of the timing (September 2014) when some schools were found closed for examination preparation holiday. 17 For Lindi, there was no sub-division. The Morogoro region was divided into 3 such categories and Shinyanga was divided into 4

18 When Form II pass rates were not available, the value was predicted by using 1) Form IV pass rates or 2) baseline results. When no data were available, the schools were assigned to tercile 2.

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