SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) is an enveloped single-stranded positive-sense RNA virus that originated in China and has rapidly spread worldwide. With the Delta variant arriving before many K-12 schools in Arizona resumed in-person learning for the 2021-2022 academic year, a plethora of mitigation measures were utilized by schools. Public schools in both Maricopa and Pima county without mask mandates were found to be 3.5 times more likely to have COVID-19 outbreaks in comparison to those with mask requirements at the start of the school year. In addition, when analyzing the presence of three other mitigation measures (cohorting, random testing, and use of improved air filtration), only 5.42% were found to use all four mitigation measures.