In Illinois, because they used the ACT in their standardized tests, we got to take the ACT for free (paid for by the school I think; Illinois is too cheap to pay for it themselves). I got a 29 on that, which is around a 1920 SAT.
Take the SAT tests as many times as you want. Generally, the more times you take a test of any kind, the better your score will be with each successive retake. I think the SAT has only 5 dates per year? The ACT has around 9.
ACT lets you take your highest score within a 2-year period and send that off to the colleges. I'm not sure what the SAT does, but I would assume they'd let you take your highest score as well.
Many colleges will need at least 18 ACT/1300 SAT before they will even take your application. Some colleges require more, depending on its prestige and standards. Make sure whatever schools you're looking at will accept your score. At 1620, you'll probably be able to get into most schools. But that was your sophomore year, right? You still have 2 more years to get that score up. So don't sweat it, and you'll do fine.
