Nick,
Yep... you are almost there. WHY the student needs extended time on a standardized test will differ with the type of disability. For a student who is LD or ADHD, they may need to understand, gather thoughts, explain (as you suggested). For a student who is blind, the extra time may be needed just to ACCESS the test (using a screen reader, dictating and checking answers through assistive technology, and so on). But you are right -- on a paper-and-pencil test, it would be extremely rare that extended time could not be made available as a reasonable accommodation. Extending… >>>