Firstly, good luck with the selection day. It's tough but certainly an interesting experience.
I don't see that your current status would be a disadvantage. What I will say is that they're going to want to see evidence of times in your past when you worked as part of a team and decision making skills etc etc so it would be good to provide examples of that from being at school. Any extra-curricular activities that you have done that promote these skills would be good to talk about too.
Hope that helps!