Can you post some pics of your chicks Sylvia? I'd love to have them to compare to my little Turken. She/he will be 3 weeks old on Monday and I have no idea what he is.
As far as the aggressive part goes, I think it depends on the individual bird. I had an ameraucana (that was supposed to be a pullet) that started fighting with the other chicks when they were 10 days old. At 5 weeks he was crowing. At 6 weeks he tried to kill another cockerel and started biting me. He wasover the top aggressive and we couldn't keep him. If you want to take the time to work with yours you can try to make him more submissive by doing things like holding him and "pecking" on the back on his head with your finger. He should lower his head and be submissive to you. There is a good article on BYC that explains how to train a rooster. Not sure if it would work in your case or not.