Yes, You should give SAT exam in Class 12th. It will be beneficial to give it by August month when you are in Class 12th. SAT Scores are used for admission into Undergraduate courses of Foreign Colleges.
Most of the Foreign Colleges start their application process in Mid August or September. So, try to give SAT on or before August mid as the SAT results are published in fifteen days and Early Admission Results of College comes by December end.
Click at this link to know more about SAT - https://studyabroad.careers360.com/exams/sat-assessments
Hope this was helpful.