We provide evidence that violence in Mexico related to the “war on drugs” from 2006-2011 had a significant negative impact on educational performance that is primarily attributable to acute psychological stress among students in the immediate aftermath of local violence. Using geographically and temporally disaggregated data we demonstrate that the largest impacts of violence on educational performance result from homicides committed within the vicinity of schools during the week immediately prior to national standardized tests. This short-term impact increases with geographic proximity and levels of violence, and dramatically exceeds the effects of longer-term violence spread over a full school year.