Many studies evaluate the impacts of Conditional Cash Transfer (CCT) programs on schooling using self-reports on enrollment and attendance even though there are reasons to doubt the reliability of these data. In this paper, we examine the extent to which school-age girls overstate their school participation. Using administrative data from a cash transfer experiment in Malawi and school attendance ledgers collected as part of the impact evaluation, we find that while all study participants overstate their enrollment and attendance rates, the extent to which this happens is significantly higher in the control group than the CCT arm. This finding implies that exclusive reliance on self-reported school participation data can lead to a serious underestimation of actual program impacts. We recommend that self-reports be supplemented using alternative sources of data on school participation that are appropriate to the experiment at hand — even if such efforts are likely to increase evaluation costs.