You shouldn't be "joining" a group of friends like a cult or something. Your friends are your friends and you don't have to pick a particular set of them. You build your own circle of friends. If they are making you choose or one group would dislike you for "joining" the other group, then neither groups would make good friends. While one group may "care" about you, they will lead you down a path of irresponsibility and immaturity. Both are pressuring you into "joining" them which is disrespectful to you.

Instead, pick and choose individual people you actually want to be friends with. If someone is going to dislike you or cast you aside for being friends with someone else, they aren't a good friend anyway. "Picking" a group makes you just as bad as them. Be friends with people you actually can connect with, share interests with, and do care about you without being immature or committing wrongdoings. Each individual person on this Earth is unique and different, so you don't have to pick a handful of them to be friends with just because they are "the group."

However, if you do insist of being friends with these people, then at least be friends with both "groups." Tell them that you're free to choose your own friends and you'll be friends with whoever you want. If they can't accept that, then it's time to move on.

You shouldn't have to choose a group. There's absolutely nothing wrong with being friends with both groups. That doesn't mean you have to mix them together or anything. Just be friends with the people you WANT to be friends with. If they're trying to make you decide, they're not the friends for you anyways, and you should seriously consider finding other people to hang out with.

Heather's right. Why should you have to choose between a group of friends? You shouldn't have to choose just because they hate each other. If you're chill with your 'preppy' group of friends and your 'break shit up' group of friends, then chill with them! You don't have to dedicate all the time in the world to just one group of friends, you're allowed to befriend whoever you want to befriend.

I don't see why you would have to choose. I think you could easily hang out with both groups of friends, regardless of the fact that they hate each other. If they are making you pick between both, then find new friends. That's ridiculous that they would do that. Friends are friends; you shouldn't restrain yourself to a specific set that you feel you need to be hanging out with. You have the free choice to be friends with whoever you please.

As others have expressed, there's no obligation to join a group of friends. Yeah, generally once people get older they will hang out with a group, but you should never feel bound to be with only certain people. Why not hang out with a little of both? Don't let pressure make you make decisions like that, because you may miss out on the opportunity to have a really good friend and that's a terrible thing to miss out on. Plus, you will probably regret ignoring the other group if you ever decide that you want to talk to them and often they will not want to talk to you because they will feel you weren't accepting of them and just left them.

I know everyone already said this, but just to emphasize it...don't choose.
You shouldn't have to choose between friends.
If either group pressures you to choose, then are they really your friends? They should be willing to be your friend even if you're friends with the other group..NOT lay down a rule like "if you're friends with them, you can't be friends with us."