Joeys not nice to other dogs

[Joey.E.CockersMommy]

Our dog Joey is becoming more a part of our family everyday. He listens to commands from myself, kids and hubbie,the growling issue has gotten much better, and will be starting obedience soon.

One thing though Joey is not good with other dogs, he tries to challenge every dog he sees male or female no matter what size, or breed. So far Joey has always been on a leash with us as we want him to have more training before letting him off. I know dogs tend to be more aggressive when on a leash, or so I have heard.

Joey lived with 8 other dogs before, and didn't like the male dogs in the house, but apparently had no problem with female dogs.

Now he is the only dog. Is he protecting us when he is challenging other dogs? Is it possible this is his opportunity to be alpha dog where maybe he wasnt before.

What should I do when Joey challenges another dog, I tell him no and keep walking, but not sure if it is actually getting through to him? :