Have you corrected her for "going after children"? Often aussies will herd running kids, that is not considered aggressive. My Gus didn't like kids much, he was well trained but I never left him alone with visiting nieces and nephews, he loved his own kids though. I think of training much more than on the agility course, to me training is a something that we do so the dog is liveable. Wait, down, sit, off, go, back all commands used in the house and they must be obeyed whenever they are spoken, don't say it if you can't enforce it. I suggest you try herding with her, she is an aussie and nothing teaches control better than herding. I also suggest to continue doing what you said which is training her in the home. I personally would desenitize her to kids screaming and running by working her obedience outside of a school area where the kids are at recess. She can see and hear them but you have her on the leash. exposing her from a safe distance can really help her learn. Also do work with her in front of a busy store, at petsmart etc. so she learns to work even with people and kids all over the place. On a weekend go to a large park and train her while the kids are playing soccer (I think it is soccer season now
) They run and yell, you can work her on leash by this activity, it will really help.
I correct for going after kids, that is one of the things that I have zero tolerance for. I'm not willing to slowly work through it with treats and games, not when kids are involved. She is an aussie and needs to know you will not allow her to charge children. Use your waits and downs for this situation. She should down on the run which is why a herding class may be right up your alley. It teaches control when faced with the biggest distraction ever. Good luck. Be firm, be patient and above all be consistant.