Another significant, but seldom-recognized problem has to do with perceptual issues. A student cannot learn if she cannot see or hear what is being presented to her. Very, very few public school teachers understand how perceptual systems—which directly affect learning—work in autistic students. For example: many (not all—remember: each autistic individual is different) have difficulties with auditory processing. It may take them a fraction of a second longer that neurotypical students to turn spoken sounds into intelligible speech, and this is just long enough to cause significant problems, as they constantly try to play “catch-up” with the rest of the class They may also find it difficult to separate the significant sounds they are supposed to be hearing from background noise. As a result, these students are often unable to follow a lecture or video, or comply with their teacher’s spoken demands. Group work is even worse, as the autistic student struggles to separate what his or her own group is saying from what is going on in other groups around the classroom. There are work-arounds for auditory processing issues, such as special seating near the front of the classroom, close-captioning for videos, the provision of both spoken and written instructions, exemption from group work, etc. But the teacher must first be aware of the problem before solutions can be found. Many a well-meaning and thoughtful teacher has caused frustration, withdrawal, even “meltdowns,” by insisting on a phonics-based approach to reading for a student with poor auditory processing skills. For such a student, a “whole-word” approach might work better. 
Other autistic kids have trouble with visual processing. They may be able to see clearly only with peripheral vision, in which case a teacher who insists that they “look at me” is actually ensuring that they will not see what the teacher is doing. Meares-Irlen, “Scotopic Sensitivity” or “visual stress” syndrome is also often present in autistic kids. Letters, words and numbers will appear to move around on the pages of a book or on a classroom whiteboard, making it almost impossible to follow what is being taught. Some students affected by this syndrome may be helped with colored overlays or tinted glasses. When these don’t work, there are other work-arounds. My own daughter, for example, struggles with math problems because of “floating” numbers. She has developed her own (admittedly, rather time-consuming) system of writing out the problems using different colored pencils for different rows or columns. The colors helped her keep numbers in their proper places. Reading on an Ipad, with a font size large enough so that only a single line of text appears on the screen can help those with this syndrome with reading. Teachers can help students find ways to deal with visual processing issues, but—again—only if they are aware of these issues in the first place.
If students can’t make sense of what they hear or see in the classroom, they will inevitably fail in school. It is up to trained specialists to diagnose their auditory or visual problems, and it is then up to their teachers to find ways to help them overcome these perceptual issues.
 On sensory perception issues in autistic schoolchildren, see Olga Bogdashina’s excellent Sensory Perceptual Issues in Autism and Aspergers Syndrome (London: Jessica Kingsley, 2003). On sensory experience in autism more generally, see J. Horder, C. Wilson, M. Mendez and D. Murphy, “Autistic Traits and Abnormal Sensory Experiences in Adults,” Journal of Autism and Developmental Disorders 44 (2014), 1461-69.
 There are work-arounds, of course, used in schools for the deaf or blind, but most autistic students are not actually deaf or blind, so these techniques may not work for them, even in the unlikely case that they are offered them.
 P. Dawes, D. Bishop, T. Sirimanna, et al. [“Profile and Aetiology of Children Diagnosed with Auditory Processing Disorder (APD),” International Journal of Pediatric Otorhinolaryngology, 72 (2008), 483–89], found that about 9% of children referred to a clinic specializing in auditory processing disorders also had a diagnosis of autism; this suggests that autistic children are much more likely to have an APD than neurotypical children.
 Leslie Broun, “Teaching Students with Autistic Spectrum Disorders to Read,” Teaching Exceptional Children 36 (2004), 36-40. See also: Kate Nation, Paula Clarke, Barry White, and Christine Williams, “Patterns of Reading Ability in Children with Autism Spectrum Disorder,” Journal of Autism and Developmental Disorders 36 (2006), 911-19; Kelly Whalon, Stephanie al Otaiba, and Monica Delano, “Evidence-Based Reading Instruction for Individuals with Autism Spectrum Disorders,” Focus on Autism and Other Developmental Disabilities 24 (2009), 3-16; Janet Spector, “Sight Word Instruction for Children with Autism: An Evaluation of the Evidence Base,” Journal of Autism and Developmental Disorders 41 (2011), 1411-22.
 Unfortunately, the scientific study of visual processing issues in autism is still in its infancy. Even the quite recent articles often fail to look beyond the most basic issues of face and pattern recognition: e.g., Marlene Behrman, “Visual Processing,” in the Encyclopedia of Autism Spectrum Disorders, ed. F. Volker, P. Pelphrey, and D. Powers (New York: Springer, 2013), pp. 3290-99. Experienced teachers may offer more reliable information on how visual issues affect schoolwork: e.g., Bogdashina, Sensory Perceptual Issues in Autism.
 The Irlen method of using colored overlays and glasses to treat these individuals remains highly controversial, but has proved life-changing for some autistic individuals. A famous example is that of the late Donna Williams, the Australian writer and autism activist.