Well I don't know if you have this or not but in my school we have a United Nations club. I don't know if that is what you are talking about, but if your school doesn't already have it, then you should do some research on that.
Now I do agree with the other two that replied previously: Make sure you find a teacher (or someone of authority) that wouldn't have a problem with starting something like that. Since there are many topics on the news, internet, and this very site, I would say that you and your friends could take like ten minutes at the start of the club to find an interesting or popular topic. After that, you all could start a small discussion/debate on it. If it is a problem, then you all could try to discuss a solution to it...
The possibilities for such a club are endless.