A lot of people don't know this but a Staffordshire/Staffordshire bull terrier are the exact same thing as a Pit Bull/ Pit Bull Terrier. The name Staffordshire is the original title given to this breed of dog and is usually used as a professional reference by breeders or organizations such as the AKC. Now as for the aggression stereotype. You are talking about puppies and no puppy is naturally aggressive, what ever breed they may be. Your puppy will nip, bite, scratch, tackle, chase, pin down, and growl because it is natural for them to do so and it is what all puppies do. What you think is aggression is simply their way of playing and interacting, and while they are puppies it is not much to worry about and there is no need for alarm. However as with children, what you allow them to do now as puppies they will most likely do once they are adults, so any behavior you don't like you need to correct at an early age. For example: If you aren't going to want your adult dog to sleep on the beds or couches in your home, do not let them do it when they are puppies. It is possible that they may be displaying dominance which should be corrected, but without seeing for myself I can not say for sure. I would recommend that you read Ceaser Millan's book 'How to raise the perfect dog: through puppyhood and beyond'. Watching his shows couldn't hurt either.