Hi all, I have three chicks that I need help sexing as our local ordinances do not allow roos. I just got these chicks from my son's school and do not have any backyard chicken experience. They are about 4 weeks old. Appreciate if those who know can tell me. I don't know their breed so I will call them grey, white and black. Thank you all 
1. Grey one
2. White one
3.Black one
A picture of the three of them together:

1. Grey one
2. White one
3.Black one
A picture of the three of them together:
