This research correlates two classroom acoustic parameters, background noise level and reverberation time, with standardized student achievement scores in elementary school classrooms in a midwestern United States public school system. Previous research in this area has shown high background noise level and reverberation time in spaces negatively impacts children's learning and performance. However, the specific levels at which detrimental effects begin to occur have not been clearly defined. The recommendation in the ANSI S12.60 Classroom Acoustics Standard for unoccupied background noise level is 35 dBA. Because many of the previous classroom acoustics studies have targeted spaces with higher background noise levels, more research is needed to determine if the unoccupied background noise level must necessarily be this low. This study surveys a wide range of elementary school classrooms to determine what (if any) unoccupied background noise level and reverberation time are necessary for optimizing student achievement.