School nurses are tasked with the critical job of keeping students safe and well. Due to competing demands for resources in schools, the impact of school nurses must be demonstrated to secure their jobs. A systematic review of the literature from 1937 to 2013 was conducted to show the efficacy of school nursing activities in American elementary schools. While some studies of immunization compliance, attendance rates, body mass index screening, vision screening, and follow-up are promising, results are mixed and additional evidence is needed. The impact of school nurses on educational and health outcomes must continue to be evaluated and more rigorous evaluation methods should be explored. Suggestions for future research and collaborations are discussed.