The content seems fine. Here are a few grammar issues to fix.
In high school, track was the most important thing to me.
With a position of power comes responsibility, and I learned about what it takes to be a leader and stand strong when others cannot.
As our season drew to a close and the team's focus shifted to the state meet, it was a stressful time as a leader.
We qualified about twenty girls to go to the state track meet, and as we ran our last track meet of the season, I felt so accomplished that with my help the team had come so far.
If you fix the grammatical errors I have outlined, I think the essay will be good enough. It's not really possible to critique you that much for ideas when it's just a general application essay about an extracurricular. You've discussed an extracurricular in as much detail as possible, so there's not really anything to criticize you on.
Fix the few minor errors and your essay should be in good shape!
Good luck!