The U.S. Department of Justice makes the following statement  regarding testing accommodations for standardized examinations: 

Testing Accommodations Standardized examinations and other high-stakes tests are gateways to educational and employment opportunities. Whether seeking admission to a high school, college, or graduate program, or attempting to obtain a professional license or certification for a trade, it is difficult to achieve such goals without sitting for some kind of standardized exam or high-stakes test. While many testing entities have made efforts to ensure equal opportunity for individuals with disabilities, the Department continues to receive questions and complaints relating to excessive and burdensome documentation demands, failures to provide needed testing accommodations, and failures to respond to requests for testing accommodations in a timely manner. The Americans with Disabilities Act (ADA) ensures that individuals with disabilities have the opportunity to fairly compete for and pursue such opportunities by requiring testing entities to offer exams in a manner accessible to persons with disabilities. When needed testing accommodations are provided, test-takers can demonstrate their true aptitude. The Department of Justice (Department) published revised final regulations implementing the ADA for title II (State and local government services) and title III (public accommodations and commercial facilities) on September 15, 2010. These rules clarify and refine issues that have arisen over the past 20 years and contain new and updated requirements. 

Below you can find links to find out how to apply for testing accommodations for the most common types of standardized testing.

SAT
https://accommodations.collegeboard.org/

ACT
http://www.act.org/content/act/en/products-and-services/the-act-educator/the-act-test/accommodations.html

GRE
https://www.ets.org/gre/revised_general/register/disabilities

GMAT
https://www.mba.com/frequently-asked-questions/about-gmat-test-takers-with-disabilities

LSAT:
https://www.lsac.org/lsat/lsac-policy-accommodations-test-takers-disabilities

Medical Board:
https://www.usmle.org/test-accommodations/