BACKGROUND: Following detection of pandemic influenza A H1N1 (pH1N1) in Dallas/Fort Worth, Texas, a school district (intervention community, [IC]) closed all public schools for eight days to reduce transmission. Nearby school districts (control community [CC]) mostly remained open. METHODS: We collected household data to measure self-reported acute respiratory illness (ARI), before, during, and after school closures. We also collected influenza-related visits to emergency departments (ED(flu)). RESULTS: In both communities, self-reported ARIs and ED(flu) visits increased from before to during the school closure, but the increase in ARI rates was 45% lower in the IC,0.6% before to 1.2% during, than in the CC, 0.4% before to 1.5% during (RR(During/Before)=0.55, p=0.001; aOR(During/Before)=0.49, p<.03). For households with school age children only (no children 0-5 years), IC had even lower increases in adjusted ARI than in the CC (aOR(During/Before)=0.28, p<.001). The relative increase of total ED(flu) visits in the IC was 27% lower (2.8% before to 4.4% during) compared to the CC (2.9% before to 6.2% during). Among children 6-18 years old, the percentage of ED(flu) in IC remained constant (5.1% before vs. 5.2% during), while in the CC it more than doubled (5.2% before vs. 10.9% during). After schools re-opened, ARI rates and ED(flu) visits decreased in both communities. CONCLUSIONS: Our study documents a reduction in ARI and ED(flu) visits in the intervention community. Our findings can be used to assess the potential benefit of school closures during pandemics.