A school shooting is an attack at an educational institution, such as a primary school, secondary school, or university, involving the use of firearms. Many school shootings are also categorized as mass shootings due to multiple casualties. The phenomenon is most widespread in the United States, which has the highest number of school-related shootings, but school shootings have taken place in many countries across the world. School shootings have sparked a political debate over gun violence, zero tolerance policies, gun rights and gun control.