Idea '04 establishes 13 categories of disabilities seen in the visual on the left. These disabilities may require special education services or may require a 504 plan depending on the academic and social/emotional needs of the student. The most prevalent of the categories of disabilities are "specific learning disability" and "speech or language impairment", which account for 54% of the 6.7 million students with disabilities  in US public schools according to the data from the 2015-16 academic year.  The presentation below defines ASD, discusses prevalence rates, data on characteristics and ways that teachers can begin to prepare for having a student with ASD in her/his classroom. The green button below summarizes the major points of the presentation. The last link of this page is an excellent resource that offers not only definitions and prevalence rates of disabilities as well as various characteristics associated with each disability, but also outlines key teaching strategies to consider when working with a student with that particular disability.