It's never too early to start studying for the SAT. I think the ideal time is actually when you're in middle school. On the other hand, I didn't start studying until 5 weeks before the actual test and I did fine. It really depends.

Well, you don't want to cram-study when the SAT is in a several weeks so I suggest getting a head start in Sophomore year, such as classes.

Sophomore is the best time. That's the time that I started studying and I took it at the end of that year. I got a 1800, which is okay, but not great. A better question would be to ask how many times you should take it.