Disability Studies in Education (DSE) developed out of Disability Studies (DS), which is an interdisciplinary academic field that questions what meaning is made of difference.  Simi Linton, a DS scholar, writes,

Disability studies takes for its subject matter not simply the variations that exist in human behavior, appearance, functioning, sensory acuity, and cognitive processing but, more crucially, the meaning we make of these variations. The field explores the critical divisions our society makes in creating the normal versus the pathological, the insider versus the outsider, or the competent citizen versus the ward of the state. (Linton, 1998, p.2)

So difference is seen as variation, not disorder.  This reflects the social model of disability, which was developed by activists with disabilities in Britain (Shakespeake, 2013) in the 1980s, and understands  that some differences are impairments, but not disability.  Disability is constructed by a world in which that impairment limits your interaction in the world.  The social model is contrasted with the medical model, which sees disability as an individual problem to be fixed.

Like many DS and DSE scholars, Linton critiques the way in which disabled people are separated (and segregated) into a separate educational system.

An entire profession, in fact a number of professions, are built around the word special. A huge infrastructure rests on the idea that special children and special education are valid and useful structuring ideas. (p. 15)

The only justification for keeping the two programs[regular education and special education] and their respective knowledge bases separate is the idea that children with disabilities are a separate category of learner. Because special education by structure and definition places disability as the major defining variability of learners, the field overemphasizes disability, milking it for explanatory value to justify organizing education into two separate systems.  Meanwhile, general education underemphasizes and marginalizes this dimension of variation in students. (p. 81)

Here is a wonderful resource to learn more about DSE: multi-media modules on Disability Studies in Education that can be used by a class or by individuals designed by my program in Disability Studies at Chapman University.