Duke University has a program that allows students to take the SAT, actually the Pre-SAT, in the 7th grade. The program is called Duke TIPS.
Any student that has scored at or above the 95 percentile of an accepted standardized test is allowed to enroll into the program.
For more information, visit the Duke TIPS website:
https://tip.duke.edu/programs/7th-grade-talent-search
Watch the video to see how 7th graders can take the SAT or the ACT: