Stanford doesn’t have enough room for all of the applicants with outstanding grades and outstanding standardized tests (as well strong essays, recommendations, ECs), Standardized tests that are below the school average will be a negative in your application. http://admission.stanford.edu/basics/selection/profile.html
Be sure that when you compile your application list that you have a solid mix of reach (Stanford is a reach for pretty much everyone), match, and safety schools that you can afford and would be happy to attend.