Sally

Question
Why does our Aussie get along with one of our Jack Russells and hates the other 2 we have? We have an 11 yr old male that Sally grew up with and gets along well with. We have a 2 yr old female we rescued and also have a 3 month old male that Sally will attack given the opportunity... We have tried the dog obedience school for 5 weeks. Nothing seems to help. On one instance we were not on our full game and Sally and Cheyenne came face to face, before we could stop the attack Sally had Chy in her mouth and Chy ended up with emergency surgery and 4 tubes sticking out of her head. Since then we've had one other situation where Sally got ahold of Chy and not biting Chy but Bit Terry's finger all the way through..We'd like to be able to keep all of our dogs together but fear we will be forced to rid of Sally or 2 Jacks. Now next situation is we have 2 houses in different states where I stay alot of the time with Sally and baby Jack.... I keep a gate up so no attacks will happen... Sally will listen to me UNTIL Terry gets here then her aggression gets bad again. We need advise before we have to place 1 or more of them.

Answer
This is not a simple situation that can be solved via internet advice.  You really should contact a behaviorist who can assess your dogs in the home, see what the dynamic really is, and advise you.  I will say that my impression is that you have too many dogs with too little training.  Five weeks is not a long time when training any dog, never mind one that is getting aggressive.  If any of the male dogs are unneutered, please have that done, as neutering does tend to reduce dog to dog aggression.
Sometimes, a lower protein diet is helpful.  Spaying should be done to avoid unwanted litters, but it seldom helps with aggression, and in some cases actually increases it between females.  It is never advisable to break up dog fights with your hands.  Instead, place an object, such as a folding chair, notebook, or something similar, in between them.  Or, use noise, water, or Spray Shield.  Until you find a behaviorist, please keep the dogs strictly separated - a bit of bluster is one thing, but injury is another, and you don't need more vet bills.  Spend the money on the behaviorist instead:-)
You can find a behaviorist on the Animal Behavior Society or IAABC web pages.