I am not sure what would happen with chickens that stayed in the coop all day together, mine free range. They only come to the coop at night. I have had several batches of chicks come throught the brooder. At about 6 weeks I lift the brooder which then becomes a grower box. The little guys can have food water and shelter and the big ladies cannot get to them. As they age, the young ones venture out of the coop. Basically all goes smooth. The little ones learn quick to stay out of reach. Usually, at about 10 weeks the young ones stop using the box and start to roost with the big ones on the big girl perches. Once they reach sexual maturity they all start to hang out together. I have had no real problems. Yes, the large ones are aggressive, but not to a point of harm. Given that they free range, the young flock has plenty of space to find bugs and greens away from the older flocks.