RESEARCH STARTER: Low-Incidence and High-Incidence DisabilitiesAlthough the Individuals with Disabilities Education Act (IDEA) lists thirteen separate disability categories, students with disabilities are generally viewed as belonging to one of two overarching groups: low incidence disabilities (LI) or high-incidence disabilities (HI). LI disabilities are rare, and do not exceed 1 percent of the school-aged population at any given time; whereas HI disabilities comprise about 10 percent of all children in public schools.