The PSAT/NMSQT and PSAT 10 are identical. 11th graders (and some 10th graders) take the PSAT/NMSQT in October. The PSAT 10 is given to 10th graders in the spring. Only the PSAT/NMSQT qualifies students to enter the National Merit® Scholarship Competition.
The PSAT 8/9 measures the same skills and knowledge as the other PSAT-related tests, but it's geared to eighth and ninth graders. It serves as a baseline to measure students' progress as they move through high school.