If you study geometry before someone else, then the test is still fairly measuring your knowledge if that is the intent of the test. If the intent of the test is as an IQ proxy, then it could be a poor proxy if the only barrier to learning geometry early is a time or resource or school constraint.
Sadly, there is a student at my son's old middle school who has no personal transportation available to take Geometry at the high school, and the district refuses to do anything other than offer an on-line alternative. In contrast, I re-worked my schedule so that I could take my son to the H.S., wait for him, and then take him back to the M.S. after Geometry. (Yeah, I'm that awesome.)
He didn't have to take Geometry and *might* have opted out if permitted. I did not allow that option, however, and required that he take the class. I did this because a.) I did not want him taking a year off from math, and b.) we already know that the i.s. on-line option does not work for us. Unfair advantage?
Imagining a fairly linear set of knowledge in math with 100 concepts numbered 1 to 100.
One group of questions on the SAT that flummoxed my son involved number theory & counting... which happened to be one of a few chapters his Algebra I teacher chose to skip
entirely.
