Low-incidence & High-incidence Disabilities Research Paper Starter

Low-incidence & High-incidence Disabilities

(Research Starters)

The categories of student disabilities are known as Low-incidence and High-Incidence. Low-incidence (LI) disabilities are rare, and high-incidence (HI) disabilities, which are more common, occur in about 1 in 10 school-age children. The number of students labeled with a disability has increased 151% in the past 20 years, partly as a result of the increased survival rate of premature babies, who are 2-3 times more likely to have HI disabilities such as learning disabilities (LD) and attention deficit disorder (ADD) or attention deficit hyperactivity disorder (ADHD). While it's relatively easy to identify students who have LI disabilities, HI disabilities are harder to assess. If evaluation comes too late, there is a missed opportunity to prevent or at least reduce the impact of the disability on the child. Two ways that students are assessed for HI disabilities are a) The aptitude-achievement model/IQ discrepancy approach and b) Response to Intervention.



Special Education > Low-Incidence & High-Incidence Disabilities


Although the Individuals with Disabilities Education Act (IDEA, 2004) lists 13 separate disability categories (Table 1), 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% of the school-aged population at any given time (U.S. DOE, 2003); whereas HI disabilities comprise about 10% of all children in public schools.

Table 1: IDEA 2004 Disability Categories

Low-Incidence Disabilities LI or HI, depending on severity High-Incidence Disabilities 1. Autism 1. Intellectual Disability 1. Learning Disability 2. Hearing Impairment 2. Emotional Disturbance 3. Deafness 3. Speech or Language 4. Visual Impairment/Impairment Blindness 4. Other Health 5. Deaf-Blindness Impairment 6. Orthopedic Impairment 7. Traumatic Brain Injury 8. Multiple Disabilities

According to the U.S. Department of Education, examples of LI disabilities include sensory impairments such as blind/ low vision and deaf/hard of hearing, physical, and neurological disabilities such as orthopedic impairments, other health impairments, traumatic brain injury, autistic spectrum disorder, and developmental disabilities such as moderate to severe intellectual disability. Examples of HI disabilities include learning disabilities (LD), attention deficit disorder (ADD), attention deficit hyperactivity disorder (ADHD), speech and language issues, emotional/behavioral disturbances, mild intellectual disability, and developmental delays. Gifted/talented students are sometimes included in the HI category because they, too, require instructional modifications to meet their learning needs. When students identified as gifted also happen to have a disability, they are termed "twice exceptional."


In the U.S., special education originated in the early 1800s as a specific area of practice. By 1948, however, only 12% of students with disabilities received special education services (McLeskey & Landers, 2006). It was not until "widespread federal involvement in the 1960s and 1970s that most students with disabilities received special services" (p. 68). During this time, HI disabilities often went unrecognized and students with LD and ADD/ADHD remained in the regular classroom without special services, while students with LI disabilities tended to be served outside the regular classroom in special schools or self-contained settings for all or part of their school day.

Jackson (2005) explains that, "in the mid-1970s, Congress voted to ensure that no child, regardless of extent of disability, could be denied a free, appropriate, and public education (FAPE) in the least restrictive environment. At that time, an 'appropriate' education meant a special education--one that was individually designed to address the needs that resulted from the disability" (p. ix). The hallmark of this legislation was the Individualized Education Plan (IEP), specifically designed by a team of educators for each student with an identified disability.

While the IEP is still in place today, its emphasis has shifted away from designing a separate curriculum with separate learning objectives toward providing access to the general curriculum through modifications and accommodations. Law as stated in the Individuals with Disabilities Act (IDEA, 2004) mandates "that no child may be denied access to the general education curriculum--specifically, the curriculum that schools and school districts make available to all non-disabled students" (Jackson, 2005, p. ix). Equal access to the general curriculum implies that all students have the right to strive for the same educational goals. "Equal opportunity implies that accommodations are in place to remove or minimize the impact of disability on authentic performance, thus leveling the playing field" (Jackson, 2005, p. ix).


The number of students labeled with a disability has increased 151% since 1989 (Ysseldyke, 2001). This increase may be attributed to the higher survival rate of significantly premature infants and advances that improve recognition of genetic and neurological factors that contribute to LI disabilities. For HI disabilities, the rate of LD and ADHD in premature infants is 2 to 3 times higher than in the overall population (US DOE, 2002). The U.S. Department of Education reports that "in the past 10 years, the largest increases in students identified for special education services were for the Other Health Impairment (OHI) category (319%), the orthopedic impairment category (45%) and the learning disabilities category (36%). Some of the exponential growth in the OHI category is the result of an increase in children identified as having ADHD, where a physician's signature is generally sufficient to trigger the eligibility process" (US Dept. or Education, 2002, p. 23).

In the United States, "22% of students with disability labels fail to complete high school, compared to 9% of students without labels" (Frattura & Capper, 2006). Less than 50% of students with LI disabilities graduate from high school with a diploma while about 20% receive a certificate of attendance (National Center for Education Statistics, 2005). Nearly "1 in 5 youth with disabilities out of school 3 to 5 years are not employed and are not looking for work, whereas 69% of young adults from the general population" find employment in the first few years out of school (Frattura & Capper, 2006, p. 356). In the 18 to 24 age bracket, only 31% percent of people with disabilities in the United States are employed, compared to 85% percent of those without disabilities (Houtenville, 2003). Not only do students with disabilities have difficulty securing employment, they are over-represented in the prison system--31% of state inmates and "23% of Federal inmates report having some type of disability; i.e., speech, learning, hearing, vision, physical, or cognitive" (National Center on Low-Incidence Disabilities, 2006).

Further Insights

Identification for Services

Since most children with LI disabilities possess sensory, motor, or neurological deficits, they are typically identified early in their lives and managed through a medical model. In contrast, children with HI disabilities such as LD and ADD/ADHD may be difficult to identify until they reach school age and begin to show signs of learning difficulties in the classroom. In 1997, during the "process of reauthorizing IDEA, the National Joint Committee on Learning Disabilities wrote a letter to the U.S. Office of Special Education Programs expressing concern that neither early nor accurate identification of HI disabilities--specifically, learning disabilities--was occurring" (Bradley, Danielson, & Doolittle, 2007, p. 8). Although there are controversies surrounding the identification process, educators agree that early intervention is key to preventing disabilities or at least ameliorating their impact in children who develop them (Jackson, 2005).

In general, SPED (special education) eligibility decisions are based on (a) whether a child is determined to have a condition (i.e., meets the criteria for one of the IDEA disability categories), and (b) whether the child has a demonstrable educational need (i.e., has difficulty learning or adapting to the school environment). It is pointless and costly to label a child with a disability if s/he is performing at grade level and does not need accommodations.

When identifying children with HI disabilities, a typical course of action is for a classroom teacher to refer the child for evaluation to determine if s/he qualifies for special services under IDEA. Evaluation is typically carried out by a school psychologist, psychometrician, or qualified special educator. Identification is typically made through a combination of teacher and parent checklists, pediatrician evaluations, classroom observation, grades, standardized achievement tests, and IQ tests. The pediatrician plays an influential role in whether a child is identified as ADD/ADHD. Sometimes a drug such as Ritalin is prescribed to see if the child improves her/his ability to concentrate on learning; the child's response to the drug contributes to the identification process.

Identifying and labeling children for special education services is a very sensitive matter. Some parents do not want their children to be identified as having HI disabilities because of the fear of stereotyping, stigma, and lowered expectations. Conversely, some parents want their children to be identified so that they can benefit from free public services. Understandably, parents are conflicted about whether to put their children on long-term drugs. From an educational standpoint, schools may be reluctant to qualify students with mild disabilities for services because special programs cost 130% more than general education. That is, if a school district spends $5,000 per student, a child labeled for SPED costs the district $11,500 per year (Frattura & Capper, 2006). While increased funding is not related to the number of children identified with LI disabilities, it does result in increased identification rates for HI disabilities. Increases in SPED funding do not seem to result in improvements in the quality of SPED programs (US DOE, 2002).

The Aptitude-Achievement Model

Typically, in order for children to be identified with a HI disability such as LD, the evaluation must reveal a discrepancy between their learning potential (as measured by an IQ test) and their academic achievement (as measured by standardized tests and grades). In other words, is the child living up to her/his assumed potential in...

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