Originally Posted by
The Don
People with a broken arm/blind don't write for themselves, they receive a scribe, they have extra time because it takes longer to communicate with someone else and tell them what you want them to put than writing it yourself. People with dyslexia have nothing preventing them from writing or doing anything themselves, they simply take longer than other people to read/write. Since the exam time is restricted so that everybody has the same conditions as each other, giving them extra time is unfair.
More time doesn't always equal better marks but it usually does. If you give a crap person an extra hour in an exam they most certainly will have the conditions to do better than if they didn't receive that extra time, they will have more time to plan out their answers and respond to the questions, so yes, time does usually equal better marks.