My cockerels stay with the flock, including the roosters and hens, while they grow, and I make decisions about them.
Any human aggression is a cull point, as are obvious conformation faults, as my keepers will be reproducing. It takes time, and development, to really see who's who out there.
I'd recommend an early cull, for early temperament issues, too small, or poor conformation. I'm not talking about SQ, but structural faults, that will matter in offspring.
Then maybe keep your best two, and see how they do over the winter.
Mary