The word “accommodation” is many times misunderstood in relation to its application to students with disabilities. Accommodation provides a method whereby a student with a disability can demonstrate his or her knowledge and abilities when traditional methods are inadequate. An
accommodation in no way implies giving someone an unfair advantage over other students.

The ADA goes on to describe that accommodations must be “reasonable.”
Three kinds of accommodations are not considered reasonable:

•    It is not a reasonable accommodation if making the accommodation or allowing participation
     poses a direct threat to the health or safety of others.
•    It is not a reasonable accommodation if making the accommodation means making a substantial
     change in an essential element of the curriculum or a substantial alteration in the manner in which
     services are provided.
•    It is not a reasonable accommodation if it poses an undue financial or administrative burden. 

Students with disabilities are required to meet the same academic standards as other students. Students with disabilities are not allowed to use their disability as an excuse to complete substandard work.

Descriptions of common disabilities here

Descriptions of commonly requested accommodations here