The rising childhood obesity rate calls for interventions aimed at improving child food choice, and one recent innovation is the use of behavioral 'nudges.' We conducted a field experiment with over 1,400 children to measure the impact of interventions based on two behavioral theories: reciprocity and theories of self-control. The interventions were implemented in the classroom prior to observing choices between a healthy and less healthy milk choice in the cafeteria. We found that small, unconditional gifts (triggering reciprocity) increased the choice of the healthier milk by 15 percentage points relative to a control group. Giving the option to set a goal (an internal commitment device) was most effective for the younger children and increased the choice of the healthier milk by 10 percentage points. About two thirds of children made a goal to select the healthier milk, and almost 90 percent followed through with their goal. We also see an impact of health information delivered by teachers. Our results have implications for policy and practice, since low cost interventions implemented at school may have an impact on what kids choose to eat and in turn on obesity rates.