Teenagers have as much power as any other age group in regards to peace in our communities and abroad.
The best thing everyone can do to make the world a more peaceful place is to look for opportunities in our own lives to enact our values; to act peacefully; to speak peacefully; to empathize.
It's easy to keep this kind of idea as a hypothetical one. It doesn't have to be.
No single person is very likely to change the world. The best we can hope for is to have a positive impact. We can do that everyday if we try. That doesn't mean that you won't have a day where you get into an argument, but it does mean that you can realize your values on a regular basis and trust that there will be a ripple effect.
But if you do want to extend yourself or participate in a more global way in making the world a peaceful place, it seems that active awareness and interest in what is happening with other people (in your own community and abroad) will often be the first step toward positive change.