Never taken the SAT, but my general experience from standarized tests (Swedish equivalent and the GRE) is that practising doesn't make that much of a difference.
I'd think otherwise.
I took it twice, on the second try I got an 710 on writing, 760 on the math, and 800 in critical reading. On the Lit SAT II I got a 750, and for US History 790.
I didn't do all that much. I had an old review CD that I bought back in 8th grade for some reason, that cost about $3, and the official review book. Nothing more. All these tutors, the expensive courses- it's all a hoax. Really, you need to understand what's on the test, and be able to think in terms of what they ask. You can study for it.
I should probably make clear that I was being a tad hyperbolic. For both tests I mentioned I did do one practice test. For the GRE they send you one when you register, so I did that. Then I read up on geometric terms in English (I've only had that in Swedish before).
I scored pretty well with that, and I highly doubt I could have done better.
It was the same with the Swedish SAT - I did 2 practice tests and ended up in top tenth of a percentile or something like that. I actually did redo it as a bet with a friend and scored lower that time.