Leadership is not just about occupying a certain position/title, it's about how you contribute. Rather than focusing on becoming president of four clubs, you should focus on committing yourself to things that interest you. I literally held no leadership positions in high school; that's just not who I am. Instead, I spent a lot of time doing two activities that interested me. I really think there is a misconception that in order to get into an Ivy League school, you must be the president of six clubs. If that were true, then our student body wouldn't be very interesting, it would just be a bunch of type A personalities arguing over positions. There is plenty of room at Penn for people who like to contribute in a group setting like in an ensemble or on a team, or people who like to do things by themselves, like become involved in research.
In high school, I always felt tons of pressure to do more extracurriculars. However in the end, I am glad I stuck with the things that were important to me rather than spreading myself too thin. I think I was able to reveal my interests and potential through my essays. I actually think that these are more important that extracurriculars.