Sound level data have been logged in 220 K-12 classrooms, as part of an investigation underway at the University of Nebraska—Lincoln on environmental conditions inside occupied classrooms. In each classroom, equivalent sound levels were logged every 10 s with an integration time of 10 s, during 36 hour periods that spanned two occupied school days, at three different times throughout an academic year. Previous presentations on this dataset have focused on average occupied and unoccupied sound levels for each classroom; this poster investigates the variation of the sound levels in the classrooms throughout the occupied days and how those differ across the grade levels measured (specifically, 3rd, 5th, 8th, and 11th grades). Among the quantifiers analyzed to understand sound level variation are standard deviation, L10-L90, and occurrence rates. [Work supported by the United States Environmental Protection Agency Grant Number R835633.]