2.7 Assessing Students with Low-Incidence Disabilities

Why This Topic Is Tested

The ETS outline asks candidates to be familiar with assessment of students with low-incidence exceptionalities, giving chronic health impairments, severe physical disabilities, and sensory impairments as examples. These students are relatively rare in any one school, so a school psychologist may evaluate only a few per year. The risk is that a standard battery, given the standard way, measures the disability rather than the ability. The central principle is simple: measure the construct you intend to measure, through a channel the student can use.

General Principles

1. Know the student's communication mode and response abilities first. Gather information about hearing, vision, motor control, preferred language (including American Sign Language), and assistive technology before choosing tests.
2. Collaborate with specialists. Teachers of the deaf and hard of hearing, teachers of students with visual impairments (TVIs), orientation and mobility specialists, audiologists, speech-language pathologists, occupational and physical therapists, and school nurses supply information no test can.
3. Choose measures whose demands fit the student. A test that requires fine motor speed is not a valid measure of reasoning for a student with cerebral palsy.
4. Report modifications. NASP Standard II.3.3 requires that any modification to standardized administration be identified and discussed in the interpretation. When modifications are substantial, report scores cautiously or describe performance qualitatively.
5. Stay within your competence. NASP Standard II.1.1 directs school psychologists to practice only in areas where they are qualified and to enlist supervisors, consultants, or referral when they are not.
6. Use functional and ecological data. Observations, adaptive measures, and performance in real tasks often matter more than a single standardized score for these students.

Deaf and Hard-of-Hearing Students

IDEA defines deafness as a hearing impairment so severe that the child is impaired in processing linguistic information through hearing, with or without amplification, and a hearing impairment as a permanent or fluctuating impairment that is not deafness but adversely affects educational performance.

Key assessment points:

• Communication mode: Determine whether the student uses ASL, a signed English system, spoken language with hearing aids or cochlear implants, or a combination. The examiner should communicate fluently in that mode, or use a qualified educational interpreter with the Briefing, Interaction, Debriefing process (Section 9.1). Family members are not appropriate interpreters.
• Verbal scales: For many deaf students, verbal subtests largely reflect exposure to English, not reasoning ability. They can describe English language skills but should not be the main estimate of intellectual ability.
• Nonverbal measures: Tests with pantomime or minimal-language directions and nonverbal responses, such as the UNIT-2, the Leiter International Performance Scale (Third Edition), or the WISC-V Nonverbal Index, usually give a fairer estimate of reasoning. Check the manual for guidance on use with deaf examinees.
• Audiology data: Review the audiogram, the type and degree of hearing loss, and amplification use. Make sure devices are working on test day.
• Language and literacy: Reading achievement in deaf students is closely tied to early language access. Interpret literacy scores with the student's language history in mind.

Students Who Are Blind or Have Low Vision

A child is often described as legally blind when central visual acuity is 20/200 or worse in the better eye with correction, or the visual field is 20 degrees or less. Educational decisions depend more on functional vision than on the label.

• Functional vision assessment and a learning media assessment, usually completed by the TVI, show how the student uses vision and whether braille, large print, or auditory media are needed.
• Visual items are invalid for students who cannot see them. Verbal subtests of standard batteries, tests normed for students with visual impairments, and tactile or auditory measures are more appropriate.
• Adaptations such as large print, magnification, extra time, and good lighting may be needed for students with low vision. Document them.
• Adaptive behavior and orientation and mobility skills are important outcome areas.

Deaf-Blindness

Deaf-blindness under IDEA means concomitant hearing and visual impairments whose combination causes such severe communication and other developmental and educational needs that they cannot be accommodated in programs solely for children with deafness or blindness. Assessment is mostly functional and ecological: communication forms (touch cues, objects of reference, tactile sign), routines, and responses to the environment, gathered through observation and team input. Some students work with an intervener, a paraprofessional trained in deaf-blindness who provides consistent access to information and communication.

Severe Physical and Motor Disabilities

For students with cerebral palsy, spinal cord injury, muscular dystrophy, or similar conditions:

• Choose measures with reduced motor demands (pointing, eye gaze, yes/no signals) and avoid timed tasks that penalize motor speed.
• Response modifications may include eye-gaze boards, switches, or augmentative and alternative communication (AAC) devices. Work with the speech-language pathologist and occupational therapist to confirm that the response method is reliable before testing.
• Motor-reduced tests of receptive vocabulary and nonverbal reasoning can provide useful estimates, but document how responses were obtained.
• Fatigue is common. Test in short sessions and note its effects.

Chronic Health Impairments and Traumatic Brain Injury

Chronic health conditions such as epilepsy, diabetes, sickle cell disease, cancer and its treatment, and heart conditions can affect attention, memory, stamina, and attendance. Many students qualify under Other Health Impairment or Section 504 (Section 10.3).

• Review medical information (with parental authorization for outside records): diagnosis, treatments, medications and their side effects, and physician recommendations.
• Time testing around medication, treatment, and fatigue; note when a student is unwell.
• Monitor change over time. Treatment effects (for example, from cranial radiation) can cause cognitive decline, so repeated assessment may be needed.
• School reentry planning after hospitalization includes academic catch-up, reduced schedules, and communication among family, medical team, and school.

Traumatic brain injury (TBI) under IDEA is an acquired injury to the brain caused by an external physical force (Section 10.1). Assessment focuses on attention, processing speed, memory, executive functioning, and emotional and behavioral change, compared with pre-injury functioning from records. Recovery can be uneven, so plans should be reviewed frequently. After a concussion, a gradual return-to-learn plan with temporary academic adjustments is common.

Students With Significant Cognitive Disabilities

For students with severe or multiple disabilities, norm-referenced tests often produce floor-level scores that add little. Useful data come from adaptive behavior scales, functional skills inventories, observation in daily routines, communication assessment, and person-centered planning with the family. These students may take alternate assessments based on alternate academic achievement standards, which also triggers IEP short-term objectives or benchmarks (Section 10.2).

Exam Scenario Pattern

When an item describes a deaf, blind, or physically disabled student and asks for the most valid way to estimate reasoning ability, choose the answer that matches the test to the student's communication and response channels, involves the relevant specialist, and documents any modification. Answers that give the standard verbal battery through an untrained interpreter, or conclude that the student has an intellectual disability from invalid scores, are wrong.