I took the SAT in 7th grade (early to mid 1990's) while I was learning pre-algebra. I scored over a 500. I did not have any tutoring from my parents or anyone else, no advanced work at school (did not get along with my teacher that year at all... probably got a C in 7th grade math the same quarter I bested the average college bound high school Junior on the SAT.)
Many of the questions do involve algebra and geometry, but you can accumulate a decent number of points with simple reasoning and arithmetic. Some of the other pre-algebra students who took the SAT with me scored in the mid 400 range, and they did fine in their algebra classes.
The inevitable realization here is that the average college bound high school junior is making enough simple arithmetic mistakes to offset the answers they get right on account of actually having studied algebra and geometry. This happens despite the obvious importance of the test.
Similarly, I worked at a bank one summer and I was surprised to find out how often career bank tellers (some with more than 15 years of experience) didn't have the right amount of money in their drawers at the end of the day. Apparently practice does not make perfect.
