Help -- how to improve SAT scores

Thank you all for your kind responses. Appreciated. My D is a junior in high school. She never took the ACT before. No idea why, though. My wife knows better but I would ask if she can take the ACT as well. Based on what I hear from all, the 6-weeks preparation sounds a stretch. She took her PSAT (1280) before but not getting better. She plans to take the SAT twice and use the best one out of the two for the college application.