Journal of Economics and Economic Education Research, v. 17, no 3, pp. 147-166. Abstract: This paper analyzes the efficiency of 465 elementary schools run by the city of Rio de Janeiro by means of a two-stage data envelopment analysis, according to the model proposed by Simar and Wilson (2007). The first stage of this study analyzes school efficiency; in the second stage, from a bootstrapped truncated regression, the variables that have a significant impact on efficiency are identified. This paper, in addition to suggestions for public policy in education, finds that higher student socioeconomic level does not correlate with higher efficiency. However, longer school days, student discipline-related problems, and the lack of solidarity programs or community clean-up programs correlate with lower efficiency.