I have not found ASD useful in my school career, especially not early on.
As another poster mentioned, I also did very well on standardized testing--likely for the types of reasons you mention: objectivity, analytical thinking, and early intuitive math skills (which are not a given with ASD, but do run in my family and seems related to ASD for us). I think these types of tests are less likely to let a subjective question slip through.
However, in class, I often did not understand the question writer's intent and would get many answers marked as incorrect because of this type of misunderstanding. Furthermore, I was often seen--behaviorally--as trying to annoy my teacher when I misunderstood her intent. To me, these tests/work and teacher requests were worded vaguely or poorly and my responses seemed to validly answer the questions. Elementary school, in particular, was quite nightmare-ish because of these problems. By high school, I was more articulate and more confident and would take my tests back to the teacher and explain my reasoning which often improved my grade. (I wish these teachers also improved their tests for future students as well.)
Have you heard of Daniel Kahneman's ideas of a two-system thought process? I think I naturally lean more on system 2 than the average person, which provides for a more thought-out, objective response. However, for most of the early teachers I had, my responses were so foreign to them, that even correct ones were judged to be incorrect because my entire line of thinking lied in their blind spots.