I have done both and both have theri merits. I must say that seperating them when the girls were in year one was good. They stayed together for kindy and have been together since year two as we moved and the school is so small they have no choice. If I had the opportunity again, I think I would seperate because it gives them the opportunity to be individuals and Imy girls are like chalk and cheese. Really they compliment each other. If you could merge them together you would have one academically brilliant child!