It doesn't work like that. You will stutter and that's completely fine. The more I worry about stuttering the more I stutter. The best possible thing you can do is relax and get comfortable. If you do find you are having a really hard time, take a couple long relaxed big breaths. If you're still really feeling bad you can take a break from speaking and sleep on it until the next day which should reset your stress. (everyone has bad days and that's fine) Big group conversations will be a challenge FOR ANYONE, especially at your age when people still have pretty poor communication skills. A good thing to do is relax and let other people do the talking and throw your word in at the correct time not interrupting people. You will get interrupted a lot, so that's a good time to take a nice calming breath, let them talk and carry on once they're done talking. The biggest thing is not to be intimidated or think anyone is too cool for you. Just chill out, don't worry and you'll be fine. Again don't worry about stuttering and don't try to hide it. You can minimize it and handle it BUT stuttering isn't awful and the best genuine people won't care about it. ​ I like to think people with a stutter have really good communication skills so hopefully you'll seem mature and cool.