Taking the PSAT test as a 10th grader is very important for honors/AP students. It will indicate if they have a decent chance at qualifying for a National Merit Award as a junior. Sophomores who score above 1300 may be able to score high enough as juniors to qualify.
Also, as with non-honors students, taking this test will give the student a diagnostic test that will indicate strengths and weakness. This will be valuable in determining how to set up an SAT program and in providing a baseline to which to compare the next PSAT and subsequent SATs.
Test familiarity increases with each testing experience. All 10th graders who plan to attend college should consider taking the PLAN test as well. The PLAN test is made by the same people that make the ACT. It tests the same skills that the ACT tests and will give you a score that would indicate how you would do on the ACT. The purpose of the PLAN is to provide the student with practice and a diagnostic tool.