Many will likely disagree with me on this, but I think High School Sports Team Captain can be overrated. Simply being named captain does not necessarily mean that you have leadership skills and abilities. Many HS captains are the son or daughter of the coach. Others are the biggest, fastest, strongest, but not the best communicators, motivators, examples, leaders, etc...
Personally, I would look for a broader range of leadership attributes across many areas. If you did JROTC, what rank did you achieve and what areas did you excel in? If you were in a club did you have a position of responsibility? Did you plan, organize, budget, recruit, raise money, and so on and so forth.
I'm sure there are many outstanding athletes that are also team captains and no doubt great leaders on top of all that. Just don't want candidates thinking sports team captains is the only leadership that matters.
Captains of academic bowls, debate teams, chess teams is a leadership accomplishment. Leadership without titles in things such as Junior Achievement, 4H, Scouting, volunteerism, etc...
Leadership is an area where many young people underestimate their contributions and abilities. Talk to your track coach. Ask about what it takes to be a captain for your school team.
In other words...
"if you want to be a knight, act like a knight" - Mark Van Doren explaining Don Quixote to his college students (Quiz Show 1994)