Puppies Aggressive Towards Other Dogs?

I have 2, 8 month old, puppies who are sisters. We rescued them from a pound, but while I walk them they always show very aggressive behaviour towards other dogs we see. I tell them shush and try to carry on walking to show I am not concerned with the other dogs, but they are big and strong and find myself dragged about. I am trying halti leads which helps me control them, but not their aggression. It is always the same one that starts it. Please help.

By Tina