A low incidence disability is a disability that occurs in a relatively small percentage of the student population and typically requires highly specialized professionals to support. The term comes from the Individuals with Disabilities Education Act (IDEA), which defines it specifically and ties it to the kinds of expertise schools need to serve these students. In the 2022–23 school year, each low incidence disability category accounted for 2 percent or fewer of the 7.5 million students receiving special education services.
The Legal Definition Under IDEA
IDEA defines a low incidence disability as any of the following: a visual impairment or hearing impairment (or both simultaneously), a significant cognitive impairment, or any impairment that requires a small number of personnel with highly specialized skills and knowledge to provide early intervention or a free appropriate public education.
That third part of the definition is important because it’s open-ended. Rather than listing every possible condition, the law recognizes that some disabilities are rare enough that most schools won’t have the right specialists on staff. The defining feature isn’t just how few students are affected. It’s that serving those students well demands training and expertise that general special education teachers don’t typically have.
Which Disabilities Are Considered Low Incidence
The categories most consistently classified as low incidence include:
- Visual impairment, including blindness: An impairment in vision that, even with correction, affects a child’s educational performance. This covers both partial sight and total blindness.
- Hearing impairment, including deafness: Any degree of hearing loss that affects educational performance.
- Deaf-blindness: Combined hearing and visual impairments severe enough that a child can’t be served in programs designed solely for deaf or blind students.
- Traumatic brain injury: An acquired brain injury from an external physical force that results in functional or psychosocial impairment. This does not include injuries that are congenital or caused by birth trauma.
- Orthopedic impairment: Physical disabilities that affect a child’s ability to participate in education.
- Multiple disabilities: Two or more simultaneous impairments whose combination creates needs that can’t be addressed through a program designed for a single disability.
Some classifications also include significant intellectual disabilities and autism in certain contexts, though autism has grown substantially in prevalence over the past two decades and is increasingly grouped differently depending on the state or institution.
How Rare Are These Disabilities?
The numbers make the “low incidence” label concrete. In 2022–23, about 7.5 million students ages 3 to 21 received special education services, representing 15 percent of all public school students. The largest categories were specific learning disabilities (32 percent of students served), speech or language impairments (19 percent), other health impairments (15 percent), and autism (13 percent). Those are the high incidence disabilities.
By contrast, multiple disabilities, hearing impairments, orthopedic impairments, visual impairments, traumatic brain injuries, and deaf-blindness each accounted for 2 percent or less. Orthopedic impairment, visual impairment, traumatic brain injury, and deaf-blindness each fell below 0.5 percent individually. When you’re talking about a disability that affects fewer than 1 in 200 students receiving special education, the practical challenge for schools becomes obvious: a given district may have only a handful of students, or even just one, who needs a particular type of support.
How Low Incidence Differs From High Incidence
The distinction between low and high incidence isn’t just about numbers. It shapes how schools deliver services, hire staff, and allocate budgets. High incidence disabilities like learning disabilities and speech impairments are common enough that most schools have teachers trained to work with these students. Strategies for supporting them are woven into general special education training programs.
Low incidence disabilities require a different model. A student who is deaf-blind, for instance, may need an intervener, someone trained specifically to facilitate communication and access to the environment. A student with a visual impairment may need a teacher of the visually impaired who can provide instruction in Braille, orientation, and mobility. These specialists are not part of a typical school’s staff. Districts often share them across multiple schools, contract with outside agencies, or rely on regional service centers.
This scarcity of qualified professionals is one of the biggest practical challenges. Schools frequently struggle to hire enough special education teachers in general, and the shortage is more acute for the specialized roles that low incidence disabilities demand. Assistive technology needs are also more varied and more expensive. A student with a significant cognitive impairment might need communication devices, while a student with a visual impairment might need screen readers, magnification tools, or tactile materials, all of which require trained staff to implement effectively.
What This Means for Families
If your child has a low incidence disability, the label itself doesn’t change your child’s legal rights. Every student who qualifies under IDEA is entitled to a free appropriate public education tailored through an individualized education program (IEP), regardless of how common or rare their disability is. What changes is the practical path to getting the right services in place.
You may find that your school district doesn’t have a specialist on staff and needs to bring one in from outside. IEP meetings may involve professionals you haven’t encountered before, like orientation and mobility specialists or assistive technology consultants. Timelines for evaluations and placement can sometimes stretch longer simply because qualified evaluators are harder to schedule. Understanding that your child’s disability falls into this category can help you anticipate these logistical realities and advocate more effectively during the IEP process.
The low incidence designation also affects how federal funding flows. IDEA allocates specific grants for personnel preparation in low incidence fields, recognizing that training programs for these specialties are smaller and need targeted support. This is one of the ways the federal government tries to address the chronic shortage of qualified professionals in these areas.