the provision of [a Free Appropriate Public Education] and cannot be considered the [Least Restrictive Environment] for that child . (6) Moreover, a principal way that sighted, hearing students acquire knowledge and skills is through incidental learning, naturally observing others and the environment. Deficits in incidental learning leave students with sensory disabilities behind in an array of skill areas. In addition to core academics, deaf and hard of hearing students, for example, must also receive specialized instruction and services designed to maximize their capacity to learn effectively and live productively and independently. Similarly, students who are blind or visually impaired must also receive instruction in the expanded core curriculum, a comprehensive array of specialized instruction and services maximizing the capacity of students with visual disabilities to learn effectively and live productively and independently. (7) The widespread use by States of the Individuals with Disabilities Education Act’s disability categories has led to a sizable undercount of students with sensory disabilities and, consequently, a lack of recognition of the extent of the systemic need for the delivery of appropriate instructional services meeting their unique needs. This occurs in large measure because students with sensory disabilities who also have additional disabilities are frequently formally classified as having multiple disabilities. Consequently, their vision, hearing, or concomitant vision and hearing disabilities and related support needs are not fully acknowledged. (8) Children who are deaf-blind should receive one-to-one services from interveners, who have training and specialized skills in deaf-blindness. Interveners play a critical role in the provision of a Free and Appropriate Public Education, because they provide access to the information these children need in order to learn and develop concepts, to facilitate their communication development and interactions in their preferred mode of