The Breakfast in the Classroom (BIC) initiative, a common approach to implementing the federal School Breakfast Program, is advocated as a method to improve students' academic performance. However, the influences of BIC on academic outcomes are unclear.To examine the effect of a BIC initiative which provided free, universal BIC on attendance and standardized test performance over 2.5 years, vs free universal breakfast served in the cafeteria before school, among students in an urban school district serving a low-income population.Secondary analysis of data from a cluster randomized controlled trial conducted between 2013 and 2016; 16 kindergarten through eighth-grade public schools in Philadelphia, PA, were enrolled and randomized to condition. Baseline data for 1,362 fourth- through sixth-grade students were provided by the school district. Midpoint data were collected after 1.5 years and endpoint data after 2.5 years.Schools were eligible in the case that ≥50% of students qualified for free or reduced-priced meals, did not offer BIC, and received programming as part of the US Department of Agriculture Supplemental Nutrition Assistance Program. Parents consented for their children to participate.Intervention schools provided BIC and breakfast-related nutrition-promotion activities. Control schools provided breakfast in the cafeteria before the school day.Student attendance and standardized exam scores.Weighted generalized estimating equations were used to evaluate differences in outcomes between conditions at midpoint and endpoint.The BIC initiative did not influence attendance (β ± standard error = .004 ± .06; P = 0.94) or standardized reading exam scores (β ± standard error = .02 ± .06; P = 0.79) after 2.5 years. Students in BIC initiative schools had lower standardized math exam scores than those in control schools, although this difference was small (β ± standard error = -.20 ± .07; P = 0.005).BIC did not improve academic outcomes among students attending low-income, urban schools.