Back to the OP's question - yes, you can prep but it only helps so much. Though folks here disagree with me on a lot of things, I think that the answers indicate that most folks plateau on the SAT score at some point, which means that prep can't get most kids to a 2400.
I think that everyone here can be "right" with their views of the SAT and ACT - different folks, different learning styles, different test-taking abilities means that what is easier for one person might not work that way for another.
A few folks said that the math sections didn't show their kid's true ability, and we saw that too. However, it showed my eldest to be good at math, even though that is her weakest subject. She is happy that she will have completed her college math requirement this semester with Calculus I (though she may take Statistics - she sees the value in that for any major). With a 730 on the SAT math and a 35 on ACT math, the mailings from engineering schools came rolling in - and we had a good laugh about her studying engineering (DH and I are both engineers).
DD18 would say that she preferred the ACT because she got a comparable or better score on it than the SAT. She studied for the SAT while she did not study for the ACT. And though she finished all sections on both tests, she would say that the ACT is cranking out straightforward problems at a rapid rate - something she is very good at doing. I realize that the speed thing is not a strength for everyone, but it is just part of the test. However she is nowhere near PG so she doesn't have the potential of many kids here. As I have said before, my kids would have higher batting averages if they were just a bit faster to first base, but you typically have to manage with your strengths and weaknesses with the rules we are given in many situations throughout life.
