Participation in the federally subsidized school breakfast program often falls well below its lunchtime counterpart. To increase take‐up, many districts have implemented Breakfast in the Classroom (BIC), offering breakfast directly to students at the start of the school day. Beyond increasing participation, advocates claim BIC improves academic performance, attendance, and engagement. Others caution BIC has deleterious effects on child weight. We use the implementation of BIC in New York City (NYC) to estimate its impact on meals program participation, body mass index (BMI), achievement, and attendance. While we find large effects on participation, our findings provide no evidence of hoped‐for gains in academic performance, or of feared increases in obesity. The policy case for BIC will depend upon reductions in hunger and food insecurity for disadvantaged children, or its longer‐term effects.