What breed do you have?
Cockerels are interesting to raise, and it takes time for them to develop into who they are going to be. Things to consider in breeding stock include issues that just having any breed rooster won't include.
Eliminate any who have physical defects, and for purebreds, who don't fit into the breed standards.
Human aggression can show up as early as eight weeks of age (had one like that here!) and has no place in the gene pool.
Keep possibles as long as you can, because behaviors will appear as they sexually mature, and you want polite individuals, both towards humans, and flockmates.
Raise as many chicks as you can, so you have lots of choices, and keep two boys if possible, not only one. Be ready to decide nobody should be kept, if that's how it works out!
Mary