The only thing that works for me is slow integration. Even at this age.:/. I had to separate a group by using a wire dog kennel. When I did this for the first time I would switch out groups of who went into the dog kennel. I have a roost in the dog kennel to give more space.
I usually keep them separated in the coop for a minimum of 4-6 weeks before putting the new group on the roost. I do make sure the youngest group is the same size as the others and able to stand up for themselves if an older one wants to challenge.
I have a bully in my oldest group. By integrating this way, she has actually accepted the younger ones. I'm on my 3rd integration in a year. I try and put the youngest out in the coop ASAP in the dog kennel. The longer they are in there separated, the smoother the integration is. I also free range and the youngest ones start free ranging at 2 months of age. They usually stay away from the older group.
My 3 I integrated this spring is now free ranging with my one year old hens. Before they hung out in their own little flock.
If I would of thrown any of them without slowly integrating, I'd have a big problem and cannibalism amongst my older hens. Once one starts picking on a chick others follow!