Given 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 more than 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 participation and child weight, we find evidence of non-random selection into the SBP. Allowing for such 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. (Contains 3 tables and 11 footnotes.)