It will not necessarily help either. The NOLS is a profit making enterprise with "Leadership" in their name and they will take anyone who can write a check for their fee. They have a good program but it does not demonstrate your leadership like volunteer things such as captain of a sports team, student council, 4H, a summer job leading a work crew, establishing a sports club, becoming an Eagle Scout, and so on. NOLS demonstrates your attendance, not documented performance. Just like taking flying lessons, because it costs a generous amount and is not available to all candidates, it really cannot be allowed to give any big boost to an application. If you would like to do their program, have the money, and would do it even if you were not applying to an SA, then by all means go for it as you will have a great time.