School participation was observed repeatedly over 2000 and 2001. Prior to the implementation of the program, there was one round of school participation checks in all preschools<sup>26</sup> . After the start of the program, there were ...ve rounds of visits in 2000 and eight rounds in 2001. The NGO ...eld sta¤ visited the schools unannounced and in di¤erent order at each round of visits. Two of the 2001 rounds of visits included school participation checks in grade 1 of primary school. Though each round was meant to include all schools, in practice some schools were missed<sup>27</sup> . The average number of actual attendance checks in preschool is 5.75 in 2000 and 6.12 in 2001, and the di¤erence between treatment and comparison schools is not statistically signi...cant<sup>28</sup> .

We use an intention-to-treat estimator to estimate the e¤ect of the program on school participation. We de...ne the set of children that the program intends to treat as the baseline children, and we de...ne the treatment as the availability of free breakfast at the school of a child’s older sibling. As explained before, school participants were systematically matched to their school’s baseline. Therefore if no school participant was matched to a particular baseline child, we assume that baseline child did not attend school. The school participation measure that we use does not make any distinction between length of absence from school or reason for absence. Children who are temporarily absent from school and children who permanently drop out of school are counted as absent. This makes sense because the line between prolonged absenteeism and de...nitive dropout is subjective. A child that has dropped out of preschool is very likely to return to school later on, either to the preschool or to primary school, so in that sense most absences are temporary. In addition, most reasons for absences, e.g. being sent home for fees, illness, lack of motivation, are potentially endogenous to the treatment. To avoid bias, we treat all absences as potentially endogenous to the program.

Matching school participants to the schools’ baselines required considerable amounts of patience from ...eld sta¤, teachers and children. If anything, matching was harder in treatment schools because class sizes were bigger. Matching errors occurring more often in treatment schools would tend to bias the school participation results downward. There were additional di¢ culties in matching school participants to the baseline. For example, Kenyan children frequently change names and families.<sup>29</sup> Therefore it is likely that a number of school participants were not matched

> 26 The pre-program school attendance visit was conducted concurrently with the baseline survey, though by di¤erent ...eld teams. In some schools, the pre-program visit was conducted after the announcement of the program, though the actual program started at least one month later. Biases arising from this are likely to be downward.

> 27 Reasons for missed visits include a national strike, ‡oods and NGO vehicle failures. In addition, sometimes visits were missed because a whole class or school had gone to inter-school games or meetings. Though such occurrences were school speci...c, they could not be avoided because all visits were unannounced. These schools were revisited later in the term if time permitted.

> 28 The treatment schools were visited one additional time at the beginning of each term, for the delivery of the food, but school attendance was not recorded during those visits.

> 29 It is common to have a speci...c childhood name, often associated with circumstances of birth. These names often

15