JENNIFER,
I agree with your conclusion -- that if students do not know the material, all the extra time in the world won't help. And I applaud your recognition of the impact time can have on testing for ANY student, and the fact that you advocate for *all* students to have "enough" time. The practical implementation of your solution (letting all students receive extended time) can be tricky in the midst of an environment that runs on schedules, limited space, and so on. But if you can pull it off -- go for it!
Dr. Jane Jarrow