This paper describes the construction and descriptive analysis of a data set of United States school shooting events. Three hundred forty-three shooting events are included, spanning 175 years of United States educational history. All levels of US educational institution are included. Events are included when a firearm is discharged, regardless of whether an injury occurs. The analysis defines a mass shooting as an event in which four or more persons, excluding the shooter, are injured or killed. It defines a mass murder as an event in which four or more persons, excluding the shooter, are killed. The data reveals that US high schools are where most shooting events occur. Relatively speaking, there have been few mass murder events in US campuses, but they have occurred with much greater frequency in the last 50 years. In most cases, shootings are premeditated. No prescription related to firearms at educational institutions is made.