I have an “advanced” 8th grade (that means they have done grammar worksheets since 6th grade) class where the range of abilities is so wide that the class slowly split over the course of the year. I tried taking the ones who were fluent or nearly fluent aned putting them into a side room to read. But they got bored and came back and then the ones with less experience resented that because while the fast ones were gone they, the slower ones started getting their mojo on and talking a lot in the TL.
So what I did then was have a meeting in which I gave them all jobs and asked them specifically what they wanted from the class. I videotaped that discussion. Then we did asstory together. The class was suddenly re-unified because each student was able to express to the others what they wanted from the class. I told them what I wanted from them as individuals as well. So in this one class everyone knew their role in the class. The result was a good story.
I will try to post that link later today. If you are having problems with superstars running away with the story, causing resentment in those who are not as fast, it might be worth taking the time to watch that class, if I can get it posted.