While the program had a positive e¤ect regardless of children’s prior attendance status, the e¤ect does vary. Children who were not found in school in the ...rst term of 2000 had average participation rates of 14 percent if they belonged to comparison school baselines and 16.4 percent if they belonged to treatment school baselines, which is a 17.4 percent di¤erence from the level in the comparison group (Table 7, column 2). Rates for children who were found in school in the ...rst term of 2000 were 50.7 percent and 64.7 percent respectively (Table 7, column 3). Both in terms of the percentage change from the comparison participation rate and in terms of absolute number of children, the e¤ect was larger for children who were found in school before the program. Additional participation among treatment baseline children was due for two-thirds to higher participation rates among children who were found in school prior to the program, while the remaining one third was due to higher participation rates among children who were not found in school prior to the program.

The overall e¤ect of the program was smaller in 2001. Children of the relevant age group participated in school 19.1 percent more often if they belonged to treatment school baselines. The estimates are noisier in 2001 than in 2000. There are several tentative reasons for this smaller e¤ect. First, the coverage of the baseline is less extensive in 2001 than it is in 2000. The sample size of children aged between 4 and 6 decreases from 5110 to 4794. Second, the ages of the children as they are reported in the baseline are probably noisier for younger children, so the sample is less well de...ned. In addition, in 2001, an increasing number of comparison schools started organizing school meals on their own, with funding from the parents. Prior to the introduction of the breakfast program, only two schools, one treatment and one comparison, organized a school meal program on their own. By September 2001, 14 comparison schools out of 25 were organizing their own meal program. This phenomenon might have been the result of a mere time e¤ect, or it might have been a spillover from the program itself that was contaminating the comparison schools.

It is possible that the implementation of the program in the treatment schools could have contaminated the comparison schools. Since the experiment was not blind, the comparison schools knew that the treatment schools were receiving the school meals. This potentially provided a signal that school meals were a worthwhile intervention, making it more likely that comparison schools would start a meal program on their own. Or there could have been a peer e¤ect or increased competition. Possibly, schools close to the treatment schools learned from the program and incorporated that knowledge into their organization. Or they could have felt the competition from the treatment schools and started a school feeding program to try to compete better. With the data available at the time of writing, it is not possible to determine what the mechanism was. Data are currently being collected on non-subsidized school meals in all schools in the district. Combined with GPS data, these data will allow us to identify the e¤ect of geographic proximity to 24