Gastroenteritis, the dreaded “stomach bug”, remains a public health concern in schools. The shared environment in school settings facilitates the spread of infectious gastroenteritis among students and staff and can lead to substantial academic disruption, arguably contributing to our nation’s mental health crisis in kids (Askeland et al. Front Psychol. 11:1268, 2020). Improving hand hygiene and surface disinfection can lead to lower rates of absenteeism in schools (Ejemot et al. Cochrane Database Syst Rev. 1:CD004265, 2008). This chapter will cover the two main types of acute gastroenteritis, their modes of transmission, and possible prevention. When the infection does start in a school-based setting, it will cover hygiene and hydration plans as well as relevant triage and disposition.