Most serious students in the US, take either the SAT or ACT during 11th grade. At the beginning of 11th grade, depending on where you live in the US, your school either gives you a PSAT or a PRE-ACT test to take sometime around the beginning of October. The PSAT test is important for scholarships because if you score in the 99% percentile you get to either a Commended Merit Scholars status or move on to the final round as a Semi-finalist Merit Scholar.
By the time most high achieving HS have finished 11th grade, they will have taken the real SAT or real ACT at least 1 time. There are exceptions, and some kids take them during 10th grade to get it out of the way.
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