Background: Secondary traumatic stress (STS) in school personnel is under-researched, with limited data on its frequency and susceptibility. This systematic review examines the extent of STS and the factors contributing to it among school personnel, defined as individuals employed or contracted by US school systems. Methods: The review includes only studies that utilized the Professional Quality of Life Scale (ProQOL) and/or the STS Scale (STSS). A comprehensive search identified 18 peer-reviewed publications (2012-2021). Findings: Thirteen authors used the ProQOL, while six used the STSS, with half of the latter reporting moderate or higher STS levels. Studies using ProQOL scoring methods found average STS levels. Limitations include a lack of sample diversity, as most participants were white (32.4%-97.2%), female (70.9%-93.2%), and teachers (12/18 studies). Many variables had inconsistent findings across studies. Other variables such as leadership practices and school safety showed significant associations with STS. Implications: These data can be used to better understand factors associated with STS and to inform the development of effective preventative and reactive strategies to reduce the impact of STS on school personnel. Conclusion: Continued research needs to occur assessing STS in school personnel to better inform best practices for prevention and reactive strategies.