travis said:what schools did you mix?.
I mixed neons and zebra danios. Before I sperated them, the neons would spin around biting at each other. After seperaing them, the neons a lot more peacefull towads eacch other, only rrarely would you see them "spinning around and biting t each other. Didn't see much of a difference in the danio behavior, but htey don't seem as "hyper-active" anymore. However, all this seperation happened during a move, and I lost 3 danios (had six, I suspect they jumped ship as I never found any courpses).
I'm still mixing beunos aires and black skirt tetras. I had them seperated before, and the black skirt tetras seemed a lot calmer and weren't feeding so aggressively (something they have to do if they wan't to eat - buenos aires tetras are aggressive feeders that even splash water out of the tank while there eating). I'm hoping to seperate them soon as well.
Personally I'm wondering how you know your fish are displaying "normal" behavior, unless you had previously kept them in seperate tanks. Although I have to agree that schooling fish will do "fine" with other schooling fish in the tank, I don't nessisarily think that's what's best for them, but I won't go around telling people that they absolutely have to seperate there schooling fish in order for them to live happy and healthy lives.