This paper assesses whether school lunches contribute to childhood obesity. I employ two methods to isolate the causal impact of school lunches on obesity. First, using panel data, I find that children who consume school lunches are more likely to be obese than those who brown bag their lunches even though they enter kindergarten with the same obesity rates. Second, I leverage the sharp discontinuity in eligibility for reduced-price lunch to compare children just above and just below the eligibility cutoff. Students are more likely to be obese, and weigh more if they are income-eligible for reduced price school lunches.