At the time when I was in the NMS pipeline, if you listed a school that you wanted to attend when you took the PSAT/NMSQT, that school would give you the scholarship if you became a finalist. The best idea was to say "undecided" and to maintain the ability to designate any school once committed.

My older brother learned this the hard way—he listed a school (October of junior year) that he decided (April of senior year) not to attend. He lost the $8k in scholarship money that he could have gotten from the school he attended—which he could have gotten had he responded "undecided".