Egg question...

For all of those who lay eggs that are of a specific breed with a rooster, and a hen of the same type, do you pen them seperately or does it matter if you want to raise chicks to be that breed and not muts with all of the other variety of chicken breeds that will be in one pen

For instance, say I want pure Australorp babies. Do I need to fence them alone in a pen( only Australorps ) away from the others or does it matter? Will they still come out the same with the other chickens. As long as the Australorps the only roo it should be fine right? Just wondering as I don't know for sure and this is something I am considering doing in the future. Thanks

vortec