In light of the recent rise in childhood obesity, the School Breakfast Program (SBP) and National School Lunch Program (NSLP) have received renewed attention. Using panel data on over 13,500 primary school students, we assess the relationship between SBP and NSLP participation and (relatively) long-run measures of child weight. After documenting a positive association between SBP participation and child weight, and no association between NSLP participation and child weight, we present evidence indicating positive selection into the SBP. Allowing for even modest positive selection is sufficient to alter the results, indicating that the SBP is a valuable tool in the current battle against childhood obesity, whereas the NSLP exacerbates the current epidemic.